but completely redoing the special effects is not a tiny little change. That is a massive overhaul, even if it is done to resemble the original as closely as possible sans the "flaws".

Well, recompositing is not the same as redoing. They'd still make use of all the layers of film generated during the original effects process - they'd just be putting the layers back together digitally rather than using the optical printer as was done originally. This would eliminate generation loss. That's all. Its the EXACT same workflow just using better tools. Its not any different from scanning the original negative and digitally colour timing it and painting out scratches and dirt. Maybe its different on a philosophical level but technically there's no difference.