p.s. i can't see the clip you attached ("no rights where i am viewing").
That is indeed your loss . . . Shakira's hips don't lie, and in fact I believe she is capable of lin kong jin . . . but that's the subject for another thread, in fact probably another forum entirely.
I think you are correct in that "it" is most clearly demonstrated with a partner or weapon. That would be where someone watching would be able to pick up on aspects of how
the "IT" exponent is moving/working, aspects which would indicate "IT". We've had a number of video clips parsed over the last couple of years, on this forum and elsewhere, as to whether Ueshiba Morihei or other video subject was demonstrating "IT."
As far as watching someone simply moving their body . . . I personally cannot discern whether that person has "IT" or not. Let me get my hands on them . . . or work a weapon set with them . . . and things become much clearer (for me).
But I don't have "IT" myself and I think that seriously limits how much I can credibly discern in others. People who do have "IT" also tend to have a highly-developed "listening" sense (in Chinese, ting jin) as well . . . seems to be part of the skill set.
Just some thoughts.