I'm trying to understand, what is being emulated?

You said it's emulation because it handles ps5's graphics APIs and unified memory. I noted that proton is also translating vulkan to another graphics API. You said it's different because the api we're targeting is proprietary and needs to be reverse engineered, implying that is the distinction. Right?

So then doesn't that imply that if we did the same thing, but without needing to reverse engineer anything, it would now be an apples-to-apples comparison with what proton is doing?