But weren’t the compositing of SFX shots redone digitally? That is every original SFX shots made of multiple layers would have each of these layers scanned (at which resolution?) before being assembled in a computer. To the effect of a better image quality (no generational degradation) and no matte lines.
So even when there’s no CGI, the digitally recomposited shots would be stuck at whichever resolution they were scanned.
Sure, but the resolution wasn’t there in the first place, because the optical compositing severely degrades the image quality. In any case for the 4K release the effects shots were rendered at 4K resolution.