are there actual tests done that way? was the "audio" power cables a simple shielded ones or did it do more?
is the evidence of a difference, evidence of which cable had the better sound?
is evidence of some differences in a given situation, evidence that there would be a difference at my house?
when we're talking about stuff protecting against a problem, we have to remember that if we don't have that specific problem(or at a magnitude that isn't audibly significant), the possibility of the "protection" doing worst than a random cable may be very real(like taking medication for troubles we don't have. they may be great when we have the problem, but that's it. be it shielding, galvanization, power conditioner, etc etc.
I've already suggested it, what's wrong with recording signals and music using both kinds of cables, and then looking at the actual differences on the sound? you're trying to make a case for how a power cable can improve audio, but none of those videos are actually looking at the audio signal getting out of devices. don't you find this a little suspicious? I sure do.
again I'm not saying that problems do not exist and that some products can't treat those problems. but if doing X meant improving audio fidelity in an audible way, it should be trivial to measure that improvement in the actual audio signal. everything else, to me at least, is blowing wind.