I once worked with an absolutely gorgeous TB conformation hunter, looked like a very well bred warmblood. His owner boarded with me and drove three hours south once or twice a month to work and show with her well known hunter trainer (also a judge).
The horse tended to be bracey on the bit, and I loosened the caveson compared to what the other trainer told her to do. The horse relaxed, his stride opened up and everything went so much better.
Until she went down for a lesson with the hunter trainer, who first complimented her on how nicely the horse was moving…and then walked over and cranked down the caveson. When she asked why, his exact words were “In my presence, all cavesons will be adjusted this way.” and the horse went back to being tight and tense.