That opens the discussion of where do you lead your horse? I lead with horse's head about 4 feet behind me and about 3 or 4 feet off to the side, so at an angle, behind. If the horse spooks, it will run forward, but since I am at the side, it should run into that open area. I can see it out of the corner of my eye if I cock my head that way a bit. If it spooks sideways, I won't get my feet stepped on.
I dont' know, this is just the way I learned. I use the line to remind the hrose to stay off and at an angle to the side. I never drag any horse, but I do sometimes have to add a bit of energy to their step, if they get "saggy" on the line.
Everyone learns things differently but in my experience (and remember it's limited) if you let the horse fall behind your shoulder, then you can't really see them, their feet are behind you and you can't control them, and if they get too slow or baulk, you can't do a thing about it.
When I lead my shoulder and the beginning of their shoulder are lined up. I can see the horse, I can let them know if they need to speed up or slow down, I know where their feet are, and if they spook, I can easily direct their bodies around me rather than through me. Again.. experience with nasty spooks while being lead from my very own Sky lol.
I've had this experience with 3-4 year olds, I've had this experience with my own horse, and I've had this experience with mature horses because they try and test their handler.
I've never gotten hurt leading a horse, ever. Never been trampled or knocked over or slammed into a gate. Nothing.
The horse's head isn't what you want to worry about, it's the rest of the horse. Those powerful hind legs, their feet, and the heavy weight of their bodies. I want to be able to control that so I don't get hurt.
Also.. your feet aren't lined up with their feet o_O That is too far back. That's behind their range of motion, and behind their shoulder IMOP. Your shoulder, lines up with the beginning of their shoulder (not your body is in the middle of their shoulder, if that happens, horse needs to back up.)
But this is the way I do it. It's not the only way, but I do think leading a horse behind you is asking for trouble as you cannot correct their speed because walking faster isn't a universal cue for "walk faster with me" it creates more distance and then you get the horse that begins to baulk or pull back.