Yeah, I don’t see Disney corporate telling Lucasfilm what to do. Especially not Kennedy with her reputation at producing great movies.
Lucas turned in treatments. That is a rough story outline that goes over the story in the broadest terms. He also had some concept art done. We know that TFA started out pretty much as he intended. We don’t know much more than that. He did come back to help with the story of TROS. As far as I know it was a meeting with him, Abrams, and Terrio to discuss the movie at a treatment level or an early draft of the script.
If you have every bothered to research how movies evolve during the writing process, you will know that what Lucas wrote out was not likely to make it to the screen. The story changes greatly as it gets scripted and then it goes through many revisions, even during shooting and editing. Movies are in a constant state of flux until the final cut is sent out for duplication. So what the earliest treatments or drafts have very often does not get into the final film. Often entire scenes are rewritten and reshot and swapped out. My DVD/BR collection is full of delted and alternate scenes that would really change the nature of the film. Some are great and I wonder why they change it and some are really bad and I’m so glad they did change it. Disney’s Tangled had an entire section that was cut but is still referenced in the end credits (parts of the story are done in a rough animation while the credits role and retell the story). Star Wars movies are not an exception.
What you see in this draft script is an early concept of the film. Most of it got dumped and evidently some of it before Trevorrow left. Was it Disney? Kennedy? or Trevorrow himself? You can’t say from the available information, but Disney is the least likely. The entire creative process used in movie making is the most likely reason for all the changes. Just look at ANH and all the changes it went through. And the ones we know of from TESB and ROTJ. And the fact that Trevarrow and Connolly still have credit on the film is testament to how the final film evolved from their original concept. Ultimately this script is a snapshot of where the movie was at that point in time. Even if this had been greenlit as the shooting script, the final movie would not have been exactly this. So if you read this and see it as what we didn’t get, you are mistaken.