No that's not it! It is more like he doesn't understand what he is talking about!
It is very simple to demonstrate his point. Use an resistant well trained opponent or even just a 100-200 lb hanging bag.
That would be a beginning in demonstrating his point.
I have not defended tgy's form and I am pretty sure he was not using his vid to demonstrate Hendrik is wrong or to demonstrate proper use of momentum and force.
You two have erected a straw man and you are whipping it with all your might to no effect because we are all know you have no idea what you are talking about.
Hendrik's vid might be an accurate explanation of W/C principles, but if it is, those principles are inadequate in real fighting.
Just about everyone here understands F=ma!
It is not that we do not understand it, it is that we DO understand it.
It is very simple Hendrik, you can begin to prove your point by using a 200# well trained person, or even just a 200# hanging bag. That would be a good start.
Anyone who has punched anything understands that maximal force is generated from the ground. That means you must have a stable base in order to generate substantial force. Force may be generated using just arms even without using the shoulders, but this force is insignificant compare to using a substantial base.
There was virtually no momentum in your actions and your alignment was clearly off as well as your timing.
If this is the best you can do, I feel sorry for any w/c person that listens to you. And no wonder they are not noted for winning any competitive fights.