I've seen one particular coach use a cycle of praise and ignoring to manipulate athletes. If they displease they are kicked out or sent to the far side of the gym to condition. If the coach is happy it's wonderful, fun, and that is what they strive to do. The exclusion makes the gymnasts more desperate for approval, and the approval when it comes makes everything seem ok again. There's no need for yelling, and the gymnasts and parents actually think coach is nice. Even coaches in the same gym don't figure it out. When they're excluded it's their fault, they did something to cause upset.
We've switched our daughter multiple times. We've seen what you're describing repeatedly, in gyms that you've heard of. A lot of anxiety comes with looking like you're a problem family, but we are simply the family that says no. Our daughter wants to enjoy gymnastics. The sport is hard enough without being yanked up and down like a yoyo dependent upon a coach's praise and mood swings. I am unable to support a coach that does not make my daughter feel good about herself.