A lot of it makes a ton of sense. But draw weight of the bow and weight of the arrows make a huge difference. Would be really interesting to see him do this even half as effectively using and 80-100lb warbow with heavy war arrows. Weaker stuff will not punch through even the worst armour at any kind of decent range. Also I wonder if this works with light flight arrows used to harass enemy at range and kill horses.

His technique does show how bad it was for the horses and why Mongols needed to bring as many remounts as they did. Battle between two horse archer armies must have been a real horse slaughter.

Also that mail shot, I bet cash that is a crap butted mail. Try same with riveted mail covered with gambeson and see what happens(nothing, this arrows will bounce like it was a wall)