All Dolby 70mm shows were mono surround unless specifically mixed for split surrounds, which only became more and more common in the mid to late 80’s-and even then was rarely used. in70mm.com has an excellent list by year that indicates where it is known that titles came in split surround on 70mm prints.
So you either have 4.1 or 5.1 technically speaking in modern channel designations, and a second sub track would really only mirror the already existing sub track. ESB and ROTJ were Dolby 70mm with mono surround.
I too think the asking was more of a formality as I don’t see how there would be any legality binding it to George’s say so since he pretty much signed over everything.