I do low level (prelim, novice) online unaffiliated dressage with my little gypsy cob (who is about as far removed from an Olympic dressage horse as you can get).
In the two years I’ve been working on schooling her (intermittently, in between the hacking, long reining, carriage driving, jumping and generally tooling about with her), she’s gone from being a downhill, heavy on the forehand, pull the reins out of your hands unbalanced ride to something with lovely paces at good tempo with developing lateral (sideways) work who is much lighter in the hand.
Schooling / dressage work encourages the horse to work more easily in their body, it’s teaching them the techniques to use their muscles effectively and when it goes right, you can feel the difference. She’s never going to be high standard because of her breed shape but she’s a million times better than she was.
It’s no different to you or I going to the gym and being coached by a personal trainer. I carry a dressage whip but it’s only used to enhance leg instructions by holding against her side in lateral work when learning moves.
What Dujardin was doing is unethical in the extreme and she deserved to be outed, can’t fault the timing of the person who had it in for her.