The GPU doesn't care about the system being on BIOS or UEFI. I had a problem where a board was using UEFI but it wouldn't take a GeForce GTX 750 Ti, which was new at the time. I had to switch back to BIOS to get it working. But does that mean the GTX 750 Ti wants BIOS and not UEFI? No, because that wouldn't make sense since I had a GTX 670 while the system was using UEFI and it ran just fine.
There are a bunch of reasons for getting away from BIOS, but they're all low level and they don't really matter to the end user. Just because you don't see them doesn't mean it doesn't do anything.