ethernet interface circuits commonly deviate from that idealized model to an audibly significant degree.
That's a design deviation or poor engineering however. I would say you have an flawed equipment problem if it loses it's composure when two spec passing cables are presented.
How many home setups use anything near the max 328 foot run? 150 foot? 75? 50?
I'll even go one further: Using the industries most stable, from many aspects and especially impedance stability, Belden 10GX would be the cable to go to for such error ridden playback devices.
What does Nordost, WW, AQ, Chord, Supra, know that Belden, a leader in high performance data, analog, broadcast cabling, with an engineering bench that is most likely larger than the entire employee base of some of these other companies on an individual basis, doesn't?
IMO there is a more than sufficient body of anecdotal evidence,
There are a lot of people that believe in the Flying Spagetti Monster, some of whom seem to be credible human beings. But the point still stands now doesn't it?
provided by audiophiles whom I consider to be highly credible
What metrics would make them highly credible for you? I think a highly credible audiophile is one that is able to validate their hearing in an intellectually honest manner.
I've tested out 3 botique cables from $27 to $233 a foot. In three systems, didn't do anything more or less than 315 foot of 5e. Also in a forum members system a $13, 100 foot cable, put the bamboozle on that members system when blinded.