well, Nvidia has time and time again dumped bags of money on devs for the ultimate optimization on their cards, while telling them to purposely mess up optimization for AMD's cards.
for instance, look at WD2 on PC, they said like back in March they were going to do their best to support AMD cards or something like that. But then the trailer for PC off of Nvidia's youtube comes out showing off all the neat things Nvidia Gameworks can do in WD2, with like no mention of stuff for AMD.
but hey what Gameworks is doing to Nvidia card looks loving dope tho, still a stuff practice at the same time.