Yeah exactly, but before they could blame Windows. Now that Windows no longer has that restriction they're explicitly preventing people from using an AMD GPU for rendering and an Nvidia GPU for PhysX. Which in my opinion is stupid since that person has to buy an Nvidia GPU anyway. I have no idea how PhysX interacts with graphics drivers though, maybe they don't want other people's driver quirks causing issues with their PhysX stuff but it still seems counter-intuitive.