This is great point. The number of different coaching styles has to have had an affect on JT. None of really know how each coach runs the QB room, but we see on the field how different the offense has been each season. Herman leaned heavily on the run game, tempo, and vertical throws. By the end of 2016 our base offense was 5 receiver sets, backfield motions, and a slower pace of the offense.
As an aside, JT is the main reason that we've even been competitive on offense the last couple of seasons. I don't understand the calls for an open QB competition. The entire offense has regressed. Neither Burrow nor Haskins nor any of the recruits would have made our offense function better in 2015 & 2016.