It's true. But it's not, at the same time. You definitely hear yourself differently, but that mostly has to do with years of having the same ear to the drummer. Your right ear is more than likely missing a lot of highs from prolonged cymbal exposure, and your left ear probably hears warmer bass frequencies from prolonged bass amp exposure. Check it real quick by snapping your fingers about a foot from your left ear, and then again with the same hand about a foot from your right ear. You'll probably notice that your right ear hears it a little bit meatier, and your left ear hears it a bit snappier.
Well, when you change sides of the stage, you're going to hear the same thing. Lack of treble, lots of white noise, muddy low mids and bottom end. Of course, it doesn't ACTUALLY sound like that, you just aren't used to hearing a different frequency range. No one put a towel over your amp, you just now have your partially deaf drummer ear towards your speaker cabinet.
