Took me a minute to figure out what you were asking, you mean your youngster is leaning on someone while he is having his feet done? Not unheard of by far, some horses have poor balance. If you know he doesn't have poor balance, than yeah he's probably just being a butt.
Your farrier didn't say anything to you about it? I find that a little weird, if Indie misbehaved about something my farrier was pretty quick to snap about it (Rightfully so, but that was a few years ago) and also didn't mind giving advice on how to correct the misbehavior.