Donald Draper wrote:
I think his motivations for turning back in at the end of the Donner Cut were more than erasing Lois's memory. Its about undoing everything. Zod never took over the world. I think the original intention with how it was written was it was a what-if or imaginary story. Everything that happens in the film is extreme for a typical Superman story of the time. Lois learning the secret, giving up his powers. But even more villains taking over the world. You never saw that in the comics, he would fight and defeat the Phantom Zone villains before they got that far.
Even so, the point is that even before they made the second film, or at least before Donner was fired, they'd already decided to put the turn-back-time ending in the first film and come up with a different ending for S2. So even if Donner had stayed on the film, S2 would not
have ended with time being turned back. Thus it was misguided for the Thau "Donner Cut" version to reconstruct it according to that rejected idea. It didn't accurately reflect what the film would have been if Donner had stayed on. And it makes it impossible for the Donner Cut to truly work as a companion piece to the original film, because of the redundancy of both films having the same ending.
And frankly, it's a lot less cheesy as well. For all the good it does, the Donner Cut also throws in the flushing toilet in the Fortress, Lois jumping out a window, extra slapstick between Lex and Otis at the prison, and a bunch of other stuff that doesn't really work.
As I said above, I think Lois jumping out a window is much bolder and more effective than the rapids sequence they replaced it with. It was a test that was far more conclusive (or so she thought), and it showed how completely sure she was in her convictions. Lois is a far weaker character in the Lester version, far more passive and less intelligent, and that's the thing that damns it most of all for me.