To be perfectly fair, we don't often know how these horses are trained and the assumption is that they're trained with welfare in mind
Before the 2012 Olympics, there was a whole
discussion on it because a video showed one rider using a controversial technique. One rider was
banned after a video emerged of him abusing a pony. I've seen people on Reddit comment that certain riders are seen as 'controversial' due to their training methods also (sadly can't remember which riders were mentioned, but it was an interesting comment anyway)
They're not exactly going to be abusing their horses in the public eye after all, so I think concerns for potential cruelty are very valid tbh