This assumes such documentation exists and could quickly be released. I very much doubt that's the case. Which means they'd first need to go assembling various internal documents, sanitize them and then shape them into a form that can be released. Too much effort for EOL hardware, I don't see any incentive to do it.
True, as all they need to do with such old documentation is to get it cleared by their legal department first, much in the same fashion AMD did with their docs. At minimum they should release the interface and programming docs (minus any 3rd party info)
However they should be able to release docs for their not quite so old cards (eg, GeForce 5,6,7)
Interfaces can still, in principle, be patented. However, the Oracle ruling is arguably the last nail in the coffin of the idea that API/ABIs can be copyrighted under US law. Frankly I'm still kind of floored that anyone thought Oracle even had a chance on that claim. 17 USC 102(b) and Lotus v. Borland were pretty big hints.
I would like to see hardware documentation for GeForce though.