It’s always interesting to hear how other people relate to their horses. I have never been in a horse situation, even hanging around full board barns, where owners are as passive in relation to their horses as the OP describes. I find it hard to imagine a rider that doesn’t know how to hang a water bucket in a stall, or doesn’t know that this is absolutely necessary even if the paid groom skives off and doesn’t do the job.
This barn sounds like some extreme of learned helplessness on the part of the clients.
I’ve been in self board my whole life, starting as a 14 year old in a low-cost backyard situation down the street where us five teen girls did all the ordering of hay and bedding, booked farrier and vets, rode without adult supervision, and really mostly did not do that badly: no one got injured, and the horses most stayed very sound. When people talk about horse ownership building character and responsibility, that’s what I think of: the kid taking on the job of being reliable, informed, and compassionate towards the horse.
I’m not sure what the payoff is in the Learned Helplessness Barn: I assume that the horse is prepped to go to shows with the riders as passengers. It’s always interesting that the more one pays for horse care, in general the less one gets to ride! I logged 6 and 8 hour days out with my horse as a teen, and figured out how to train her to do things on my own, and had a very good time. But we were certainly on no show circuit.
Anyhow, if you have turned over every aspect of horse care to an all-controlling trainer, I don’t even know what the point of asking for training advice on a forum would be, because if we give advice that is different from what trainer says, you’ll never be allowed to do it.
I would want to see the kick before I decided what to do about it. If the horse was out on 20 feet on longe line, and bucked up, and the back end just kind of tended in a little, I’d say high spirits. If my horse sets up bucking on the longe, I know she is overdue for turnout, and I go let her rip at liberty.
If the horse however made any move that seemed like he was actually threatening, it would be a Big Deal and I would correct it on the spot with the degree of force that particular horse required.