Re: internal strength demo...
Ark is the guy in the grey track suit.
Now that we have a video for reference, once again; the way I do this is to stand with my hands straight out and in a neutral stance. It looks like I should just fall over backward, I then let the other guy stand in a fighting stance and try to walk trough me with our hands out straight.
Again as I said I don't "move" anything. At various points I bounce them, or plant them so they can't move at all, and all you see is me doing little body adjustments.
All that said, it's a test, so it all depends who's playing with who as they are learning.
And one more time, so as to be clear. I offered commentary only to outline that those methods are a much more clear way to eliminate any possibility to jujutsu being applied. It's all internal. Even then it goes from basic jin to more sophisticated body skills.