A very interesting topic, indeed.
The topic starter in his video spoke about plenty of questions. I would divide them into two areas - pure mechanics and power generation.
So, at first my two cents to the pure mechanics.
Where does it come from. The topic starter is a russian guy and there is a common discourse in the russian boxing theory, antinomy punch-push. The main things as I remember are speed and collision time. A punch is fast, a push is slow. A collision time is not less important. A punch has a short collision time, a push has a long collision time. When a collision time is too short and transfer of energy does not occur, it is not a punch or push. it is a touch. A relatively slow blow with a short collision time is still a punch, but a relatively fast blow with a long collision time becomes a push. That is why returning motion is so necessary. Of course differential time is split seconds.
Let us go now to kungfu&karate strikes. Let us take for consideration a straight punch. Most common, as it was said, it has some "freezing" at moment of impact. It automatically makes this strike a push, that is why topic starter says "no punches in kungfu". It does not matter so much for weapon strike and he supposes that such unarmed strike is only imitation of
weapon thrust and furthermore "kungfu" itself is a "translation" of weapon techniques to the unarmed combat.
I would add, watching a real TCMA, it has no strikes into head, all strikes and defences are for the body. It makes not much sense if we do not suppose that these techniques are quite recently evolved from weaponry techniques.
If we make digging into history, all striking systems come from weaponry styles. The old english boxing comes from fencing, there were much more body punches, and using of parries similar to hard karate blocks. So the old english boxing was much more akin to kungfu&karate, than to modern western boxing, and it is a question for serious analysis what alterations came from using the gloves and what from further evolution from armed to unarmed combat.
Nevertheless, it remains a riddle for me with that "freezing", it is something unique, what it is its real purpose? Even with the weapon, it is more chances to miss than to hit, because most time the opponent is lucky enough to take a defense, and it is better to return to guard position. The only possibilities I can think of, that it is for learning purposes or for performance. I saw a pair of chinese masters, they return the hand with grace many pro boxers can envy.