Well, that's one possibility, though not the one I hold. I think SOME people can hear the things they claim to hear, and some have superior hearing and can hear things that others may not.
I think some other people THINK they can hear things that aren't really there, and aren't aware of just how poor human auditory memory is or how much the mind can influence our hearing.
Yet other people will agree they can hear things that they KNOW they can't, just to avoid looking like a tin-ear.
Which of these a given person is, I have no way of telling unless I know the person well. And the test to *prove* one can really hear something (blind ABX) is a pain in the ass, and even MORE so (maybe even impossible) for something like differences in guitars.
As to this specific subject, I can't hear any difference with MY guitar I've tried it with, through MY rig, with the pickup I've used. That's pretty specific, and may not apply to others' guitars, pickups, rigs, or hearing. But my logical guess is, if there IS difference, it's a very subtle one. I would suggest anyone trying it to record the guitar before & after, and change nothing in the interrim. Maybe still not a perfect test, but a better indicator than trying to remember what it sounded like minutes ago (that sounds funny, but auditory memory is very short - SECONDS for subtle differences).