The actual Special Editions (the 97 theatrical releases are really the only ones that are actually “Special Editions,” everything else is just Star Wars) seemed a lot more concerned with “fixing” things, and a lot of errors were tackled. The Special Editions were also on Fox’s dime, entirely. Some of the more egregious additions to the Special Editions were done as a sort of testing ground for prequel effects, but the SEs did do a decent job of removing “mistakes” from the original releases.
You’re right however that the 2004 DVD release and the 2011 blu-ray release (which were Lucasfilm budgeted, I believe) were less about fixing anything and more about adding stuff if they could. Those releases didn’t really have the same mandate as the Special Edition did, and likely had a smaller budget. So the idea there was different, and the execution reflects that - those releases are definitely more along the lines of “put that thing in there, that’ll be cool” instead of “here’s a list of errors I’d like cleaned up.”
I don’t think the 1997 SE was on Fox’s dime. Lucas wouldn’t have let them get a claim on TESB or ROTJ that way. The SE’s were edits more than fixes. Did they actually fix a single real issue with any of the films? No, only things GL had problems with. He had a vision of what it should be and the SE’s were to mold the films to that vision not to fix any mistakes. The Hoth snow scenes recomposition wasn’t really necessary. It is nice, but not necessary. The audio changes weren’t necessary. The films was fine without the Wampa. The windows in Cloud city were added in some shots and not others creating continuity issues. The three times he touched the films he kept doing that same thing. The only real gaff that he fixed was the Tie-Figher holes on the falcon in ROTJ. Everything else was editing. He didn’t fix a single mistake in ANH (and there are a lot of them). Adywan’s revisited actually fixed the things that needed to be fixed.