My own main concern with GamePass as a model is how sustainable it would be, let alone what actual net profits it could bring in, for companies
not Microsoft if they were to implement Microsoft's approach 1:1. Let's face it; GamePass is likely not bringing in a ton of revenue or net profit for the Xbox division at this time. When Phil Spencer said it's sustainable, he meant that Microsoft as a whole has the size to incur any losses from operating the service in growth phase, which is 100% correct. That's because there's only one other company in the entire world of Microsoft's size, level of revenue, net profit, and resources, and that company's name is Apple.
A lot of people seem to be saying Sony should take Microsoft's lead, make a GamePass for PS and put all their games on it Day 1. Make all their games Day 1 on PC.
This would effectively kill PlayStation IMHO, because not only is PlayStation much more important to Sony's bottom line than Xbox is to Microsoft's, but Sony don't have the level of resources or money to continuously incur losses on a GamePass-style model for years at a time. The losses they saw with PS3 alone were enough to put them in jeopardy of never releasing another game console again, because it, among other things, completely wiped out their PS1
AND PS2 profits!
If Sony were interested in pursuing a truly GamePass-like model, there's only two real options for them in order to make it work during a growth phase that doesn't severely impact their overall revenue and profits. The first IMO is to do things like bringing their new releases Day 1 to the service, but wherein you're still effectively paying for the full game. Just that your payments would be broken up into monthly installments, so your upfront cost is cheaper while still getting you the full game. These kind of versions of the games would need some type of DRM built into them that can then be removed once all payments are cleared, the owner would need to check in once a month to make the monthly payment. But other than that, they'd have all the same rights as if they purchased the game in full Day 1.
On the PC (& mobile) side, they would need to establish their own launcher/storefront, or enter some incredibly lucrative partnership with someone like Epic or CD Project (GOG). Something where they can retain 100% of profits from 1P sales, and get their 30% from 3P sales. They'd probably also want to do something where they can monetize the launcher/storefront with ad-supported free model, and stackable tiered options (I think they should do this with the rumored Spartacus too, where you can build your sub in a-la carte fashion) offering various perks like free monthly games, PS1/2/3/PSP/Vita BC with streaming, maybe Crunchyroll and digital film VOD perks etc. That way they can control/stabilize any drop-off in console sales with the users going to PC and using the launcher/storefront, either in its free form or subscription-based form, buying and renting games through that.
Sony's other option, if they still wanted to have an answer to GamePass that's sustainable for them, would be to partner with a larger company, or potentially enter a merger. Because they would need to be able to sustain operating losses doing things in the same way Microsoft is doing for GamePass, and they can't do that as they are currently. While they aren't the only option, a popular one is probably Apple. And in truth, this would be a
worst-case scenario for Microsoft, so the people saying Sony should do a GamePass of their own...if it's not like the stuff I was saying earlier, you better realize that this option would not be to Microsoft's benefit much at all (if that's something you care about).
Otherwise I don't particularly see why they need an answer to GamePass but I don't see the same arguments being made for, say, Nintendo. Sony as a corporation brings in more than 2x the net income as Nintendo, and PlayStation contributes a decent bit to that (as does mobile). Their strategy for gaming growth seems to be in using live-service games as their multi-platform presence, at least some of them. They probably don't want to jeopardize their brand image or selling power by making everything they are multiplat or PC Day 1 (if ever), because if that has a perceptible impact upon hardcore fans and they stop buying the hardware, it can impact revenue of 3P developers who rely on PlayStation as a major source of their revenue.
So it's not just about Sony, here,
they have to consider the needs of their 3P partners as well. Unless they have a digital storefront/launcher on PC that can effectively serve as a replacement for the physical PlayStation console (meaning the vertical integration Sony have with PlayStation and its ecosystem would have to be duplicated on the PC side), then it would be a net negative upon their bottom line and brand, and also hurt 3P developers. That could cause a rapid spiral and make them an also-ran in the console gaming market, all from what'd basically be a self-inflicted wound.
There's also no guarantee that 3P devs and pubs would be able to make up the lost revenues & profits from a severely depreciated PlayStation install base (due to many leaving because of Sony putting all their games, especially non live-service GaaS titles, on Steam Day 1 or shortly after launch on PlayStation) through Xbox (since that would have a similar situation) and Switch (wherein native versions might not even be possible due to hardware limitations). I'm curious how something like the FTC could see such a large negative impact in overall console gaming market revenue coming about, because Sony were otherwise goaded into pushing for GamePass features and PC Day 1 the exact same way Microsoft does it, in a manner where alternative revenue streams for 3P partners could be ensured. But I'd imagine they wouldn't like that and could see it as grounds for a wider investigation into the practice of services like GamePass and even Microsoft's acquisitions to push GamePass growth, if they felt it was warranted.
Sony, Nintendo and Microsoft have to follow their own paths to ensure success. Microsoft's found theirs, or at least they're in the process of doing so, but that isn't really Sony's path. If it is, and to be in a way that doesn't actually severely damage Microsoft (seriously; Sony teaming up with or entering a partnership with a company like Apple to push their own GamePass alternative is likely Microsoft's worst nightmare, and for good reason), then they would still need to take soft steps and only truly start committing to it if the prospect of manufacturing consoles in the future to meet demand looks grim.
Otherwise if Sony panics for whatever reason, and just starts reacting for the sake of reacting, they risk making the same mistakes SEGA made when systems like the 3DO, Jaguar and, yes, even the PlayStation, entered the market. Instead of capitalizing on their strengths (arcade gaming, merging the home & arcade closer together through not just cohesive hardware but also services), SEGA tried replicating Sony's strengths and paid the price for it. Now they're a (pretty strong) 3P developer and publisher because of those mistakes; there's probably some people who look at this crossroads (well, it's not really a crossroads) for Sony and are gleeful about supposed karma or whatever, but
there's no actual reality for Sony where they're "paying the price" for anything; the PS brand's stronger now than it's ever been and their revenues & profits are higher than they've ever been, too. Their 1P is effectively top-of-class in the industry in many aspects, and even their other divisions like film are stronger than they've been in the longest time.
The only karma Sony as to pay is if they go carelessly chasing after companies like Microsoft when they have no reason to. I don't agree with some of the "analysts" out here, I don't think the market is significantly changing in ways companies like Sony and even Nintendo aren't prepared to make adjustments for. In the meanwhile, they can gradually prepare for a stronger presence on PC, a means of doing Day 1 there and on a service, that doesn't leave them up shit's creek if console owners start gravitating to said options en masse, financially speaking. Because like I said right at the start, Sony doesn't have the resources or sheer corporate size of a Microsoft.
They have to play this smarter, not harder.
EDIT: Notice I didn't even answer the OP's question but hey they figured to answer it themselves in the OP. Not that I actually agree with that answer btw; we'd need more actual releases to come about before seeing if there's a patter to support OP's idea. So there's almost no point in making statements like what the OP has done: we literally don't have enough games released yet to prove one way or the other