I'm currently unable to view the links, but I am familiar with such videos showing monks, martial arts masters, etc, doing pretty amazing things with so-called "chi."
I have no doubt that human beings are able to perform outstanding feats via training, concentration and whatnot. The old saying that people use only 10% of their brain? I think it's more accurate to say that people use only a fraction of their mind-body potential. Anyone who has ever experienced "being in the zone" will understand this. One's performance with anything--mental, physical-- when in the zone does appear "superhuman," if you will, when compared to the semi-conscious clunking around state in which we normally live out lives.
That said, the problem I have with chi is this: my impression is that people see chi as a particular form of energy, something above and beyond the normal, measurable energy our bodies put out (eg, heat, bioelectric field). Ie, "chi" is a term identifying some kind of particular energetic "substance." IMO, this is a wrong interpretation.
Let's keep in mind the basic definition of "energy": the capacity to do work (regardless of "substance"😉. I think it is more accurate to interpret chi as what happens when a person is able to focus the various forces our body can generate (ie, electrical, mechanical, etc) into a single, coordinated effort. Eg: drying a towel? I don't see this as the result of some kind of esoteric energy substance, but rather the mind and body working in unison to affect the body's machinery which generates heat. That is, via concentration--or better, meditation--one's mind can access those aspects of physiology which us ordinary, untrained folks can't.
I hope this makes sense (I rambled more than I intended). Basically, chi is not so much an esoteric power field as it is ordinary biological functioning brought to optimum/maximum intensity via psychological direction.