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"