Nope, its not in the newest leaked drivers (6.31).
Its possible that it could be an enhanced register combiner set, though I would think they would not have made a completely different named extension out of it. I would also suspect it would use the concept of “programs” so that you can more easily reconfigure it at run time with a single call, and it would probably also have a performance advantage.
Just went and redownloaded the document to try and re-read the context in which NV_fragment_shader was mentioned, to see if maybe I could pull something out of the wording. Strangely enough, I cant seem to find any reference in the document to NV_fragment_shader. It looks like it has been removed from the document (and the document was edited several days after it was posted). Did we all just make this extension up? Also strange is that I now noticed a reference to NV_texture_shader. While its possible I might have missed it, I dont remember seeing this before. Maybe they renamed it. Anyone else know? I’ll have to look when I get home and see if I might have saved a copy of the original version of the pdf.