Thanks very much for the response. I'll have to educate myself on those references.
This article is helpful for someone like me, because a meaningful technical explanation does far more for me than someone just blindly asserting that I'm not hearing what I think I'm hearing. The problem is to understand what you are trying to say, you really have to dive deep into the technicalities. I mean, Fourier analysis alone takes most people weeks of study to appreciate, even with a year or two of college calculus under your belt.
The problem you face is the people who sell this stuff often have simpler explanations that seem to make intuitive sense. For example, with the jitter point, they'll say something like "Of course we're not saying bits aren't 0s and 1s ultimately, but you know timing matters. It's not just about whether all the bits get there but whether they all get there at the right time! Even a slight delay will affect things like spacing of the soundstage." And that sounds plausible to many people. E.g., I don't think I appreciated what exactly SNR and THD measurements mean until I read your article, and that, yes, they should pick up these kind of timing delays. (Although to be fair I'm still not sure why only the sum of the 1st 10 harmonics is used in THD and whether this has any implications for the measurement, but I also haven't yet read the posts you cross referenced when you mentioned that).
Understanding Fourier takes some study, but most folk understand a frequency plot and mange to get the general idea.
I expect most people will not bother to put forth the effort to read even these simplified articles and continue to "poo-poo" anything but their ears. Fortunately sites like this exist to help those like yourself who really do want to go further and not just blindly follow the marketing adverts. And many companies produce ad copy that hits some fundamental truth but is misapplied to audio, or ignores the reality of how the circuits are actually implemented to spread FUD. Audiophiles do not understand how say Ethernet data transmission works, or how modern DACs resample the clock and obviate whatever fancy clock scheme people add in front of it, nor should they (I am certainly no expert on Ethernet links, but know some of the basics), and marketeers prey on that ignorance. It is not the fault of the consumer; I wish there were better ways to report false or misleading advertising not requiring thousands or hundreds of thousands in lawyer fees.
Ten harmonics for THD is an industry standard. By the tenth harmonic, it is essentially noise unless something is wrong. BTW, SINAD is the measurement I use, because it includes all noise and distortion. But, while it provides an "easy" single number, you must dig deeper to obtain critical information for your system. Is it dominated by noise, harmonic distortion, jitter, power supply harmonics, ??? A single number does not tell all. What it is useful for (to me) is weeding out things -- if the SINAD is 40 dB (1% error), I probably wouldn't bother to look at it. If it is 100 dB compared to another product at 110 dB, then I want more information to compare the products.
At the end of the day I am not really fighting the people selling stuff, nor consumers who have no interest in any sort of objective measurement. I hope to help knowledgeable "lay" people, interested audiophiles, and fellow techies who's expertise lies in other areas by showing some of the details behind the measurements and technical verbiage.