Thanks for explaining, I'm so used with the original stereo track, that even minor things like that tends to distract me. But I agree that it's one of the cool additions heard in the mono track.
I think the '93 remix additions, the sounds of debris whizzing by the cockpit or the laser-impact near Threepio at the escape pod, are 1980 sound-effects created for Empire.
Anyway, I like what I've heard so far very much :) haven't done a complete listening yet.