Would you ever mount a horse that was tied up? If the horse had a tendency to fidget or shift about, would you tie him up, then reach forward undo the headcollar and ride off?
Yeah in Portugal there was a 12hh pony we used to do that with. He was fiendishly difficult to mount from the ground or a mounting block, even with someone holdhing his head, so we'd have him tied up with a headcollar over his bridle and then undo it when we were on board. He never pulled back or fidgeted when done this way, not dangerous with him, it would be more dangerous to try and get on him in the middle of the yard...
Never, ever, under any circumstances. Would rather spend 23 hours a day training the horse to stand than do that. Extremely dangerous idea.:frown: