I have a young horse (3 coming 4) and I do 99% of the rides. We’ve had some very young assistants at my barn and while I’ve been open to letting them ride him, as soon as it started to not go well I very nicely asked that the head trainer be the only one to ride my horse. It wasn’t a big deal but I didn’t want him being allowed to get away with things or have the assistants going to him war with him.
Sometimes I find that young trainers feel like they have to prove a point and don’t know when to quit…which can be quite counter productive when training babies.
In my scenario I’m older, more experienced, and ride just as well, if not better, to help put it in context.
EDIT: to answer your question - I’m the only one that’s shown him so far but I would only allow head trainer to show him at this point.