I don't even get why there is a debate on whether hiyaw exists or not. I think it's just like food. May food na may "hiyaw" dahil sa uri ng ingredients meron ito (say, locally sourced organic whatever = superior tonewood and materials) at sa nagluluto nito (Michelin starred chef = luthier) at sa pagkaluto nito (technique = craftsmanship). Meron din namang food na may "hiyaw" kahit hindi superior lahat ng aspects nito dahil sa quality ng total mix ng mga elements sa pagbuo ng pagkain (think your grandma's home cooking).
Is it qualitative? Of course.
Is it quantitative? Definitely not (and this is why the debate even exists). Give the exact same grilled chicken ingredients and exact same recipe and technique to a home cook and Bobby Flay and I can guarantee that the Bobby Flay will have the grilled chicken with"hiyaw."
Is it universal? Yes, but it takes people who can discern the quality, similar to how chefs can distinguish fresh shrimp from frozen while ordinary people cannot. These chefs have experienced these in person, similar to how firemodel claims you should go to his place and check his stuff.
Can you show it through the internet? I don't think so. Similar to how I have followed an Alton Brown cookie recipe to the letter, including the exact weights, grade of flour and butter-sugar ratio and cook and rest times and whatnot, but it barely looked like the one in the picture and obviously didn't have the expected texture.
The point is, there's no reason to debate whether hiyaw exists or not, and firemodel trying to prove it through videos or records won't do anything to back up his claims. You both have to be there with your guitars and his guitars and use the same amps and cables and rooms. Then only can you judge if you think hiyaw exists or not.
IMO you can only start debating about the existence of hiyaw if you have played both non-hiyaw guitars (which is the default case) and guitars that are claimed to possess hiyaw.
End of story.
(FWIW I think hiyaw may exist, but only because the same concept of "universal exceptional quality" exists in other non-quantifiable aspects or disciplines, like the aforementioned food example. I can't say I believe in it yet though, because I haven't even had the chance to play better guitars through capable equipment)
P.S. as a recording enthusiast I also agree with firemodel that hiyaw, if it exists, cannot be captured by recording, as recordings are inherently "lossy" and highly dependent on the character of the microphone, preamps, A/D converters, sampling frequency, mic placement, etc. (ask a recording engineer what half an inch does to sound).
