I think it is a holdover from the days when nobody knew what the 70mm mix of ESB sounded like, but this idea that it was similar to the SE, or to the 16mm, or the 8mm, or to any other odd variant is incorrect. Examination of the in-theater 70mm recording by morgands1 shows clearly that the only version the 70mm mix resembles is, in fact, the 35mm.

The 70mm version was made first, with the 35mm being completed shortly thereafter to go along with the visual edits. They are both extremely similar throughout the movie and show only minor differences from each other: a few small sound effects changed, a few level differences, a few lines of different ADR at the very end, etc.

It doesn’t make sense to think that any of those major differences in other versions would have appeared in that first mix, been completely deleted from the second, and then somehow reappeared in subsequent versions. Just like the changes to the mono mix of the first movie, all that extra stuff was added much later. The 70mm and 35mm share a common 4-track source in their ancestry, and are therefore very similar in any part that wasn’t re-recorded for the 35.