I look forward to your demonstration. But think we’ll have to disagree on this.
Imho, a poorly designed headphone cannot compete with a well-designed headphone, even if they measure similarly at the DRP. EQ just can’t fix all the things that can be wrong or detrimental or limiting to good sound in a poorly designed headphone.
Your argument seems to be that most of that other stuff is just inaudible. And FR is always the dominating factor. That hasn’t been my experience with the various headphones I’ve used. And I’m also leaving out things like positional consistency, microphonic effects, and probably a number of other factors that are unlikely to show up on a single FR plot.
If you’re comparing two similarly designed and performing headphones though, then they may sound alot alike with some EQ applied. I don’t think I’d argue with that.
I also think that some sow’s ears can be improved with EQ. But at the end of the day they will still be sow’s ears, and not silk purses… regrettably.