As I understand it, Bob Gale watched all 3 BTTF movies with the new transfers and approved them. The movies were also approved by Amblin. Granted, this isn't a perfect process - you've caught an error that proves he wasn't paying attention to the end credits on the first movie. And no, I strongly doubt that Gale was looking at every frame with a magnifying glass. But these guys do sit down to watch their movies to make sure they like the way they're being presented.
You're absolutely right that we've seen recalls and corrections in the past, and we'll continue to do so. I'd add that problem with the Star Trek TNG S1 blus, which is the most recent situation of that kind I have seen. I didn't know about the Star Wars LD mistake, but I do know that there are plenty of fans who are quite unhappy with many other changes Lucas did make... (That's partly a joke - I know how big that can of worms is...)
I've also found a few websites that track alternate versions of movies. It's a heck of a rabbit hole once you jump into the various home video and even theatrical versions of movies.
Just as an example, JAWS:
1. Theatrical Release version from 1975
2. Cable TV version from 1980 (?) - Pan & Scan, radio music replaced
3. VHS version - Pan & Scan, radio music replaced
4. Discovision Version - Pan & Scan, radio music replaced
5. Laserdisc Version - Pan & Scan, radio music replaced
6. Widescreen Laserdisc Version - Letterboxed (non-anamorphic), radio music replaced
7. Signature Laserdisc Version - Letterboxed (non-anamorphic)
8. Widescreen VHS Version - Letterboxed (non-anamorphic)
9. DVD Version - Anamorphic Widescreen, new 5.1 sound mix
10. Blu-ray Version - HD Widescreen, new HD sound mix (albeit with mono mix included on disc)
If we did a tracking of this for the Star Wars movies, with all the various different cuts and tweaks and changes, we'd be here all day and all night...