I an in a unique (sadly) position to weigh in on this. For reasons that I don't feel like recounting right now, I have spent a lot of time with professionals "adjusting" the way I hear. I have also spent many hours as a research subject participating in studies relating to human perception of timbre and pitch. I am not going to claim that what I am saying is a fact, it's my take on the subject and take it as you will: A/B comparisons of sound are very very tricky. When I go to the optometrist and he/she puts me on the machine and starts clicking lenses "1 click or 2..." I can instantly perceive a difference and only at the end of the process, when differences are small, I might need a repeat. Not so for hearing. As Ron pointed out with his Hendrix comments, there seems to be a LOT of some kind of auditory memory/overlap/expectation brain processing going on that makes it much harder to do "A or B?" The ability to hold an auditory perception for a long period seems to be difficult so the whole "swap bodies/pickups" tests seem compromised.