Plausible deniability?
I don't know that it's a diabolical plan hatched in a black tower at NV headquarters. However, I do know that NV code has once again significantly negatively affected the performance of AMD cards on a game. I also know that NV contractually prevents a dev from working with AMD to fix the problems the AMD cards have with the NV code. I also know that in this case, from what is being reported, AMD was prevented from even having a chance to do anything from having this game being fundamentally broken on the majority of their hardware before it was released for review.
It does all come under the heading of circumstantial evidence. There is no single damning piece of evidence that NV is actively working to sabotage the performance of games on AMD cards. However, when the evidence continues to pile up, year after year, at some point the evidence, even if circumstantial, begins to present an overwhelmingly compelling case.
If NVIDIA is in bed with this many developers they must be hung like a horse