I can't give details on how we do our selections (not nvidia but another gpu manufacturer). But we do have direct contacts into a lot of studios and we do try and help them fix their game if possible before ever putting something in the driver to fix it. Studios don't pay us, it's mutually benefital for us to improve the performance of the games. It also help the game run better on our cards by avoiding some of the really slow stuff.

In general if our logo is in the game, we helped them by actually writing code for them, if it's not then we might have only given them directions on how to fix issues in their game or put something in the driver to tweak how things execute. From an outside perspective (but still inside on the gpu space) nvidia does give advice to keep their competitive advantage. In my experience so far ignoring barriers that are needed as per the spec, defaulting to massive numbers when the gpu isn't known ("batman and tessellation" should be enough to find that), and then doing out right weird stuff that doesn't look like something any sane person would do in writing shaders (I have a thought in my head for that one, but it's not considered public knowledge. )