What you are missing is that is a circular argument. How do you know that the test says a lot about the harmonic distortion that will be reproduced during music ? Because you reason that it does. You are your own validation. It sounds like science because it has numbers and test devices, but in reality it is not scientific.
What you are missing is that you tend to make a lot of (il)logical leaps and assumptions when arguing with others. And though you did not state it explicitly, this quote right here is the equivalency of saying, "I don't understand basic principles of science or how to apply scientific results and analysis to the real world." (Consider this...
music is sine waves. If ONE sine wave at any frequency produces HD, it logically and scientifically follows that a collection of multiple sine waves played at the same time will also produce HD, and likely even at a greater magnitude than one sine wave...multiple sine waves also bring in the topic of intermodulation distortion. This should not be difficult to accept considering you were quick to assume most people in the $120 Vali thread didn't listen to a wide variety of music based on even larger logical leaps.)
If you don't believe me or think I'm just pulling this all out of my a** to support what I'm saying, fine. I know I'm no expert despite all I've learned so far, but you have mentioned earlier (and unintentionally make it clear in your posts) that this topic is not one you're entirely up-to-speed on. If you are so unsure about these topics (you did ask "How do you know...?"), you really ought to research them more before
trying to call others out.
But, as such, the topics of T50RP driver limitations vs. larger, often more technically competent ortho (or not) drivers generally seen in more expensive headphones, whether or not this even matters based on the limits of human hearing, how this factors into pricing and value, etc. are getting OT and best served elsewhere.
I'm also a really big fan of the T50RP driver, FYI, and was part of the DIY community when the Paradox was just a whisper and the Mad Dog did not yet exist (I was much less of a modding contributor and more of a learner). Just because I recognize its technical limitations doesn't mean I don't also recognize how amazing it is. It's not quite a top-tier driver, but it's arguably one of the best value-to-performance propositions you can find in terms of drivers.
Apologies for being OT, but I hope what I've said about the T50RP driver does not make one enjoy the AD or any other T50RP product any less (because it shouldn't).
I also want to make it clear that while I appreciate measurements and do use them as a tool, my current setup is using a NOS DAC. That should say something about my approach to all of this (if you don't know why or what a NOS DAC is, consult teh Googs).