Well from my dads advice and following It for nearly 30yrs I can say neither myself or a horse I have been riding have decked it.
If you look at his head he has lowered it and stretched it out, if I had held on to his mouth the his head would be curled under therefore not allowing him to use the heaviest single part of his body in order to balance out the rest.
People may dispute what my dad has told me but considering it has never brought me a sore one then I'll continue to follow it.
Kia and I have both but the dust once in 16yrs, he slipped and lost both back legs cantering out a hack. He tried his best to stay on his feet bit when 2/4 have gone sideways the only way is down. He didn't hurt me, roll over me or trap me and he got up without standing on me and considering I was right underneath him when he got up that was quite a feat for him