Having heard the posted recording of the 70mm mix, I arrived at a similar conclusion to that posted by Belbecus--that the '93 mix is, in fact, primarily based on what was used for the 70mm, but with additional sound effects added in. The similarities are too great for it to be anything else. What tipped it off for me was the sound of the wall exploding as the stormtroopers blast their way into the Tantive IV--on the '93, compared to the '85, there is much more bass in the explosion, but it sounds less 'powerful' somehow because of the way the the higher end frequencies are mixed in. The '93 and 70mm are identical in this sound effect, as I had suspected.

Great find, Belbecus!