You think it could be a psychological experiment? It is possible to play something for someone, then tell them changes have been made, play the same thing for them, and the brain plays tricks! Stupid brain, I was pissed at mine the other day so I attacked it with a Q-Tip through the ear canal... That'll teach it a lesson it won't soon forget! Or maybe it will?
People can hear what they believe has been done :-) I doubt that Alan is this diabolical? I'm pretty sure he made some changes, although, the extent may have been subtle. But I've seen people react differently on different days to the exact same recording? So I know this is how our brains work (or don't?)