It's an interesting subject, regardless since Sony is so tight lipped on how the OS functions (in comparison to the info MS has released). MS was definitely more forward thinking here. Especially if Sony isn't even using a software container, which regardless of quick resume, would at least allow them to spin up a different OS image for older software etc. I guess they might have to keep all the old libraries available forever going forward for back compat. Whereas MS can chuck the works if they like for new software and just run the old game OS for the dated software.
It's possible they are already using virtualization and not saying anything.
But containerization just doesn't work the same way; Sony could be using that too.. but it wouldn't enable a system-wide feature like Xbox has. They do have the ability to watch a video while playing a game, almost like the original Xbox One "snap" with the tutorial thing. That might be using containerization, in fact..pretty likely. So I retract my laugh at that lol
The "tricks" on Linux that enable sort-of-works-sometimes "dump an app" using process pausing, and then attempt to successfully dump the objects the app is referencing in memory to file. Then attempt to re-load that and un-pause later.. but because the entire state of the system isn't actually paused, it's.. far from full proof. Even just pausing/resuming a process w/o dumping to file is not full proof on Linux or Windows. Virtualziation also doesn't make it full proof, but at least the state of the kernel is also paused.
If a game supported "save anywhere" and auto-saved any time you exited out, they could present a "card" in Sony's UI, and have you jump right back into the action. That would be an easier way to do it, and require far less hard drive space, as only that save file would be needed.
Most games, particularly on console, don't really support true "save anywhere" though. It's usually "you can save, but when you load the game back up you aren't actually loading right where you were, just the most recent checkpoint." Particularly when you are in a mission; games that do have an explicit "save" option often disable it during missions.
That's the nice thing about quick resume; and what's nice about using "rest modes" too. I used it a lot on my PS4 Pro because I much prefer just being EXACTLY where I left off when I stop a gaming session, rather than having to load to the last checkpoint.