Yup, I just checked it and that shot is the one with the huge gash right through R2D2, it looks like the tear was held back together with glue. That's why it is so DVNR'd to death for the 1993 master, to hide it, you can't even see it on the GOUT. No doubt this would have been replaced for the 1997 with a replica from an alternate source, and this is assuredly the reason for the framing difference, although the precise reason might never be known (e.g., whether the alternate source itself had a shifted framing, whether they had to shift the framing for some other technical reason like edge damage, or whether they just decided to shift it for aesthetic reasons).

What's weird is that they could shift it one way or the other in both the 1977 negative and the 1997 negative. There isn't any more top/bottom room (the 2004 release does have a hair's height of opening up vertically, but it's like that throughout, it's just a normal thing that happens from transfer to transfer), so that means the shot hasn't been blown up uniformly. It doesn't make sense why there would be so much extra horizontal space in both 1977 and 1997 versions. Was the 1977 negative actually a dupe blow-up to get tighter framing and the 1997 version went back to the wider original camera negative? If so, and they tried to match the tighter cropping, then why abandon this match by shifting the image horizontally? Aesthetics? It does look better centred. I dunno, it's weird, but it has to do with the torn original negative, I know that.