Again they didn't specifically mention fastballs, in fact, an example Kaplan used was Robin supposedly questioning A.J. on why he called a change up on an 0-2 pitch.
That being said I do think there was something going on behind the scenes with A.J. I do know that one high level member of the front office lost "all respect" for him (direct quote) after the incident in Minnesota when Young threw that forearm to A.J.'s face and he simply turned and walked away.