I sat at one of their facilities once and listened to a few iterations of some circuits. Guy varies the signal path distance... and the sound changes.
So your eyes were involved in that experience. It makes sense, right? That the longer distance would make things worse.
A component he deems more thermally resilient vs non-resilient (external solution)...the sound changes
You don't know that the sound changed and neither does he or he would show it to you on an audio analyzer or scope.
He had no engg explanation as to WHY himself? (Why Flippin why?)....
Why indeed. Both of you perceived a change. No question there. The question is whether the output of that device changed or not. This is what we are interested in. After all, we don't listen to music through you two's brains.
The explanation is that our hearing is dynamic and bi-directional. Your brain decides from moment to moment how much it cares about detail in the music. Most of the time, it has to throw away 99.999% of what it is hearing as recording everything would take infinite storage. But ask your brain to analyze things and it will then go into a different mode and listen much more carefully. When it does, you all of a sudden hear more air. More detail. The soundstage opens up. All of these things happen. But they happen with nothing changes in your system! You changed.
Once you hear that change, now bias sets in. You listen to the "before" system and the magic is gone. You listen to "after" system, it comes back.
What is incredible is that even full knowledge of this effect won't make you immune to it. It is so part of being human that it is just going to happen.
This is why we test blind. That way, you don't know if a change has occurred or not due to randomness of selection.
When I first started to test Marantz AV products, performance was worse than Denon. I asked the company why that is. They said they have a guy just like what you are describing making changes and a Golden ear guy makes decisions on what sounds best. I told them that process only works if the testing is done blind and repeated. Fast forward two years and Marantz products now have excellent performance with none of that degradation through the methods you describe.
We (science) are not stupid. Doing blind tests is hard. But we have to do it to eliminate not only bias, but above elasticity of human perception.
A great example of this: one of the ex-stereophile editors (now part of Absolute Sound) lives near us and he was kind enough to invite our local audiophile group to go to his house and listen to his system. While there, he had a new amplifier for review. Room was too small so we split up into two groups. First group went it and heard comparisons of his everyday amp against the amplifier under review. They come back and without saying anything, our group goes in. We are presented with different music samples played by both amps. At the end, he asked which amplifier sounded better. Majority (not including me), voted that one was.
We come back as a group to meet up with the first group. As soon as we got there they asked us which amp our group said was better. Guess what? We had selected the exact opposite of what they had! Jaws fell on the floor in both groups. Both were so convinced they were right.
The reviewer then said he knew why that happened. He said that he played the amps in opposite order for each group! In other words, merely changing which amp went first vs second, determined the outcome. Not the fidelity difference!
He was partially right. As I mentioned above, it is often that the second sample sounds better due to us paying closer attention although this doesn't have to be this way.
I didn't vote as I mentioned above because there was no way to make a proper comparison. And at any rate, both sounded similar anyway.
While what you experienced makes lay sense, and you were impressed by an authority that you thought knew more than you, what I am explaining likely does not. But it is a proven fact not only in audio but in many other fields where blind testing is performed.
So I am asking a lot. I am asking you to put aside your intuition and limited experience and trust the science. You do that to believe earth is round even though every bone in your body says otherwise. No way do you want to believe that time changes with speed yet we have GPS satellites that are calibrated for this based on Einstein's theory of special relativity. You have to trust the science in audio much like you do in other areas. Otherwise you live in a sea of confusing opinions about audio.
These are things I have explained in my video tutorials:
Let us look at a less extreme case. I have been tied to a violin for 40+ years. I own a few different violins. I could record a progression on 2 different violins I own. You play it back and I will pick out which violin is which without blinking.
I have address this before. Those two recordings could be shown trivially to measure differently. Here, you all are claiming differences that you say are not measurable so best not to mix examples. Even here, we would need evidence of y you doing this reliably. I show how I can tell extremely small impairments in the second video above. This is done through record of double blind test. Countless audiophiles failed that test.
Bottom line is this: there is not a single professional society that would accept the results of any non-blind/uncontrolled testing as you say you have done. You claim superiority to the science but lack any evidence to prove it. Only self-appraisals under an alias in a forum. That, doesn't amount to anything.