Okay, I think we are now at the point where we can say we have discovered a few things about THX that have been misrepresented in ‘common knowledge’ of THX’s history.

On Home releases, before the film begins, the Director’s Cut shows a trailer from the SF-series “Buck Rogers” episode “Tragedy on Saturn Chapter Two” (1939). According to imdb, the theatrical version had a segment from the S/F-film “Things to Come” (1936).

False: I have now seen 4 separate prints, all from 1971 that have the Buck Rogers intro , not ‘Things to Come’.
It would appear that the story that the 1971 release had ‘Things to Come’ as the intro, and that was later changed to Buck Rogers is incorrect.
Also interesting is that if you listen to the Buck Rogers opening, Lucas changes the audio from “The 25th Century” to “The 20th Century”, to make it more poignant which also supports it not being a ‘last second replacement’.

That WB butchered Lucas’ version of the movie, making him remove ‘X’ minutes from the film, which is why it failed at the box office.

False: Comparing the 1971 release to his 1978 release and the Home Video versions, whilst there are some differences, there are actually very few changes, and there is some extra footage of SEN with the children in the 1971 release. There certainly weren’t enough changes to alter the film in any tangible way, apart from humanising SEN a little. This also fits with Coppola’s claim that Warners barely touched the film for the intial release.

We can confidently now quantify the changes between the 1971 and 1978/Home Video releases, which up until this point were not known/recorded.