That’s not a Disney thing, really - that sort of thing almost never happens at any studio. And if it does, it only happens DECADES later.
Part of the reason “The Beginning” was so remarkable back in 2001 was because people DIDN’T do that for new movies. And Lucasfilm never really did it again, either. And “The Beginning” was still somewhat sanitized.
People love behind-the-scenes drama - but the people who have to still work in the industry once the drama is over don’t love it very much, and they don’t love having a salable version of it available at will for consumers to memorize, either. So those sorts of “warts ‘n’ all” documentaries and tell-alls are for later, when that effect diminished, and there’s a lot of distance accumulated.
it’s not a question of Disney trying to appear squeaky clean, it’s more that nobody wants their dirty laundry from work aired out like that.
The documentary on “The Last Jedi” was refreshingly honest for that sort of thing, and sort of surprising that Disney/Lucasfilm was okay with the “Mark Hamill hates what they’ve done with Luke” narrative. I think it has more to do with Rian Johnson, who seems to be more of an upfront filmmaker who’ll explain his creative process, influences, etc. JJ is a much more guarded filmmaker when it comes to the creative process and also seems more of a company man, even if he may have been frustrated by the experience of Episode 9. But of course it makes sense for Disney to try to sweep any creative difficulties under the rug.