Actually back in the 1800's it wasn't at all uncommon. Even in the early to mid 20th century it wasn't too uncommon either.
If someone hasn't been around horses and doesn't really understand horses it's best to stay away from them
Especially the hind (back) end.
As a teen working at Belmont Racetrack here in New York during the mid 70s, I once got licked in the butt by a super high-strung 2-year-old colt named Sky Messenger.
I can’t believe I actually was able to recall his name. I can’t even remember where I put my reading glasses most of the time!