You didn't address the things I brought up, Rob. Are you saying that reactance and resistance leakage have no perceivable effect? Maybe they don't. I'm not attempting to prove that they do. I'm just considering possibilities. Personally, I don't care one way, or another. As I said, the test I linked to is good enough for me.
One thing I do know is that analog filters do not have completely smooth slopes. There is some subtle wavering along the slope, particularly along the low end cut off in a HP filter. Perhaps it varies with different cap voltage levels (mass), or materials? That may account for some of the differences people hear? I don't know, and I'm not prepared to make a definitive answer one way, or another. You smell me?
Does learning to make the best of what you have require learning how it functions?