OTOH, how likely was it that a guy whose timing and pitch selection is messed up was going to unwind it instantly just by decreasing his latitude by one degree?
You can look at it as two competing ideas about his problem. If he hadn't gotten into bad habits, if he was doing everything the same as he was before he was called up, then sure - he'd go to Toledo and instantly be back to where he was, but the implication of that would be that he simply couldn't hit MLB pitching doing the things that had gotten him to the big leagues. I don't think that is a conclusion I'd like to see verified.
OTOH, if he was a player who had gotten out of sync with himself, who had things he had to fix to get back to better, you might expect him to have work through that over some time even once the pressure of facing the best pitching was reduced.
I'm here all week. Try the veal.