I dont have an opinion about direction but the problem is way more deep than the skeptic would want to admit....
Or you are complicating a ham sandwich. There are two choices. The difference is audible. The difference is not audible. The only way to know is an unbiased listening test. No more. No less. If a person is making the claim the wire is directional, then you test that 1 person, with that 1 wire, and if they cannot tell the difference, then their claim is debunked.
--- Don't be confused about what the claim actually is. They are not claiming that wires are directional. They are claiming that they can hear the difference in the direction of wires. --- We are not debunking the directional claim, we are debunking the claim they can hear a difference.
If we do this test enough, then we can draw a statistical conclusion that they are not audibly directional, in all likelihood for anyone. However, by measuring the properties in both direction, we can make fairly accurate claims as well. If the difference is -120db below the signal in the audible frequency range, we can be confident it will not be heard. We could be confident at a much smaller difference.
But still, most of the claims are made by very specific people, i.e. manufacturers, who claim the difference is obvious and significant. I don't remember ever hearing this before manufacturers started claiming it. So, given their extraordinary claims, we only need to debunk their ability to detect a change. Not everyone on the planet, only their claim, which is that they, as a company, can detect directionality. It is a well bounded case.