Whenever I see a video that claims to show internal power all I see are biomechanics. To me internal is about using intent, not just overt biomechanics.
Fortunately, for many demonstrators the average viewer can’t see to see the biomechanics involved, be as obvious as they are to all but the blind or those who chose to believe and be blind.
Below is an example of what I mean by using intent :-
You might notice that I am standing in a stance. I stood this way to make a point to my student about taking the body structure out of the equation to isolate the intent.