Why wouldn’t this run on an actual ps1 or spx?
Lot of people know how to work with Unreal Engine 4, but PlayStation was programmed in C. And you probably want MIPS Assembly as well for hot areas in terms of performance.
I don't see that render distance feasible on PSX as well. The Bloodborne of PlayStation was the Nightmare Creatures series and render distance was way closer. And of course you want to throw some loading screens here and there, PlayStation RAM bus and CD 2x cannot stream a game like that at that speed.
The demake also doesn't exhibit jittering. To get something like that you want to tessellate way beyond the PlayStation capabilities.
It's pretty much like Shovel Knight on NES, it looks like a NES game, but no, it surpasses every limitation of the console.