Fair enough, Jody, but I did make the distinction between the inchoate form and the finished work, and also the role an artist’s oeuvre might play in granting a special status even to unfinished work. (As for the title: How else am I going to get those RSS feeder readers to click?)
As for the note cards themselves: Are they a collection of random lines, narrative arcs, snatches of dialogues, or do we have chunks of fully rendered prose, which in and of themselves would be of historical value?
I am sympathetic to the late writer’s wish to determine what is or is not fit for publication, especially since, as you point out, unfinished work is, well, unfinished, and was never in the “public domain” to begin with. But if it was that simple, why is the son having such a hard time of it?