Couple thoughts (from the first part of the video)
1) Being super tense and doing isometric super tense holds of the movements or sets of slow tense movements are not going to add explosive power in striking. In fact, tension is something you should try to avoid as much as possible if you are after power.
Power is about developing maximal mass transfer, maximal leverage, and maximal speed. Yes, you need to have enough strength to support the force coming back into you and the more you have the more force you can theoretically therefore transfer into the opponent. But practicing like they are isn't a good idea IME.
2) All of this stuff seems impractical to use. A real opponent isn't going to just stand there and let you knife hand them or palm heel them in the neck/chin. They are going to be moving around, many times will have their hands up and ready to defend (which would render much of those techniques ineffective).
Or, if they are just standing there with their hands down, you're pretty much going to jail for assault or perhaps even murder if you just haul off and start chopping their throat or gouging their eyes like that. Much of the stuff that they are doing looks like the WW2 combatives stuff, which was designed for battlefield application (where it's pretty much anything goes and kill or be killed), not for civilian self defense application.
The person would have to have pretty strong evidence that their life was in immediate danger to justify using those tactics. Especially since the guy is practicing them from a casual stance and then aggressively engaging the attacker.
Why not just try to put distance between the two of you while talking your way out of it in that case? Why not try to use postural self defense/de-escalation tactics to try to at least make it seem like you don't want to partake in physical violence?
3) His non attacking hand is kept low and down leaving him wide open to counter strikes. Let's see him strap on some MMA gloves and get into the ring with another fully resisting (and skilled) attacker and we'll see how effective his stuff is and how practical it is for active combat.
Oh, but I bet they'd argue that it's "too deadly" to train with resistance right? In the case of things like weapons training that could be a valid argument (though, even in those instances there are generally methods which allow for close approximation and therefore more accurate testing), but most of the time with unarmed stuff it just means that people have never tested their stuff and are afraid that it might not work (and make them look like less of an expert).
No sir, I don't like it.