Interesting, his techniques would've been very useful to horse archers from the Steppes but less so for the Medieval English bowmen who shot at long and medium ranges and enthusiastically used mauls, swords and daggers up close.
I'm skeptical of his piercing mail and the gambeson underneath, I suspect he used mail that wasn't riveted (and he was shooting at <very> close range). During the Crusades the bows of the Turks and Arabs had great difficulty penetrating European mail and the chroniclers describe unharmed Crusaders looking like pincushions, with several arrows stuck in their mail but none having penetrated.
I think this guy is portraying the bow as some sort of ancient assault rifle. But I think his ideas have some historic merit; Steppe peoples such as Scythians, Parthians, Turks, Mongols and such grew up in the saddle with the bow and being herdsmen would've had plenty of time to develop refined archery techniques.