There no point on a GPU schematics and for sure they will never be released.
I'm not so sure about this.
The value is in the chip itself and not in the PCB, nor the connections, and I would not be surprised if those GPU manufactures have application notes on how to use their chips available, but I'm a naive guy.
I'm also confused why you'd want those schematics. Let's see, there is a pci expres bus to the PC, a video connector on the output, a few memory ic's and a chip which does all the rest. If you study the datasheets of the support circuitry you'll probably get a fairly good idea how everything fits together, but you have probably already done that.
Loui Rossman gets his rotten fruit schematics from a program I believe is called "boardview".
I have a vague memory of "laptopschematics.com" or similar.
But sources with that kind of detail/quality of information tend to need to be fed with silver to release their particular order of one's and zero's.