Yes, it does, but it gives the rationalization that Matt was previously an artist of an underground comic strip, whereas Brooks and Simon were both well-known TV execs and writers. Also, the book claims that while there was some animosity between some of the writers, including Simon, it really didn't pick up until all the merchandising checks came, and it was revealed Matt was making much more than anyone else.
But you really shouldn't be surprised that Matt isn't into the creative side of the show that he gets the credit for. I really do like Matt, but it's been obvious for years he really doesn't do anything, except for creating the initial characterizations of the Simpson family(even these were later tweaked by the writers). Even characters like Krusty, who was created by Matt and inspired by a TV clown from his childhood, didn't have their personalities created by him, it was the writers, led by Sam Simon.
It's kind of like even though Walt Disney is famous for starting the highly successful Disney studio, the only thing he really did of high importance creatively was create and voice Mickey Mouse(even then, him creating Mickey Mouse is up for much debate).