NVIDIA can resort to paying developers to only optimise for NVIDIA performance and/or cripple AMD performance.
https://techreport.com/news/14707/ubisoft-comments-on-assass...
"Radeon HD .. gains of up to 20%.... Currently, only Radeon HD 3000-series GPUs are DX10.1-capable, and given AMD’s struggles of late, the positive news about DX10.1
Ubisoft’s announcement about a forthcoming patch for the game. The announcement included a rather cryptic explanation of why the DX10.1 code improved performance, but strangely, it also said Ubisoft would be stripping out DX10.1 in the upcoming patch
Ubisoft decided to nix DX10.1 support in response to pressure from Nvidia after the GPU maker sponsored Assassin’s Creed via its The Way It’s Meant To Be Played program."
https://techreport.com/review/21404/crysis-2-tessellation-to...
"Unnecessary geometric detail slows down all GPUs, of course, but it just so happens to have a much larger effect on DX11-capable AMD Radeons than it does on DX11-capable Nvidia GeForces. The Fermi architecture underlying all DX11-class GeForce GPUs dedicates more attention (and transistors) to achieving high geometry processing throughput than the competing Radeon GPU architectures."
GameWorks slowing down ATI/AMD users by up to 50% https://arstechnica.com/gaming/2015/05/amd-says-nvidias-game... https://blogs.nvidia.com/blog/2015/03/10/the-witcher-3/
(In the way they use their devs to help AAA games to fix some issues under some circumstances, there had been cases where optimizations speed up Nvidea but hindered AMD due to architectural differences but, surely it was all accidentally).