If the genres did not exist before, by assigning labels Ishkur changed that, forever. Of course it is full of snarky satire, but truth- and insightful nonetheless. Regarding made up artists, I wouldn't be so sure. It's certainly possible, but the set of obscure artists is immense. Even the set of obscure artist personas of one person can be incomprehensibly large.

If some of the music was just written for inclusion in the guide (which is entirely possible from my point of view since I can identify many, but not all of the examples), how would it be less real than anything else at the bounds of near-infinite obscurity? It would just be another "artist" backed by the same person or collective as the Ishkur handle, just like the numerous incarnations of Bangalter.