There are also DLL mods that convert nvidia's DLSS API to AMD FSR, in which case games usually need to be fooled into thinking the GPU is made by nvidia and not AMD
I've heard of Intel Arc users for instance not able to play certain games because it checks for AMD/nVidia, so you'd have to fake the GPU vendor to get it to work.
That is usually more incompetence than malice. They write a game that requires different operation on amd vs Nvidia devices and basically write an
If Nvidia:
Do x;
Else if amd:
Do Y;
Else:
Crash;
The idea being that if the check for amd/Nvidia fails, there must be an issue with the check function. The developers didn't consider the possibility of a non amd/Nvidia card. This was especially true of old games. There are a lot of 1990s-2000s titles that won't run on modern cards or modern windows because the developers didn't program a failure mode of "just try it"
I was also confused about this. I didn't find an article talking about yet either. My current assumption is that it is just this game and that it is still a closed pre-release. So they maybe just wanted to remove noise from people that don't have the required specs during their testing phase. It's also not a lock to a specific GPU vendor as I originally expected from the title.