Little Bob was not posing. That's the thing worth knowing about this photograph.
A band stallion's job is almost entirely defensive. He isn't the leader in the way people assume: in most wild horse bands an older mare decides where the group goes and when it moves to water. The stallion's role is perimeter: watch the horizon, watch the other stallions, and put himself between his family and whatever he doesn't like the look of. When one stands still and faces you for twenty minutes, he is not being photogenic. He is assessing you, and he has positioned himself so that you have to get past him.
Knowing that changes how the picture reads. The stillness isn't calm, it's evaluation. The ears, the angle of the head, the squared-up stance: all of it is a stallion deciding whether the thing with the tripod represents a problem, while his mares graze somewhere behind him, out of frame and deliberately so.
Which is also the argument for the long lens. Fifty feet is not a legal requirement, it's a working minimum that keeps the animal's behaviour honest. Get closer and you stop photographing a wild horse and start photographing a wild horse reacting to you.
On printing this one: this is a portrait that needs room around it. The composition already has air on both sides, and cropping in to make the horse bigger would throw away the thing the frame is about. That he's standing between you and something you can't see. Hang it with space around it and don't let it fight a busy wall.