I think it’s more the other way around. They designed the feature around their new hardware as a form of competitive advantage. Most of the time, you can exchange cross platform compatibility for better performance.
Look at CUDA vs OpenCL, for example. Instead of improving OpenCL or making CUDA an open standard, they instead double down on keeping it proprietary. They probably get a small performance advantage here, but the main reason they do this is to secure their monopoly. The same goes for GSync vs FreeSync, but it seems they are backing down and supporting FreeSync as well.
They want you to think it’s a pro-consumer move, but really it’s just a way to keep their competition one step behind.