Only way to disable this is to open about:config and change some value. Why this has no dismiss button?
There is couple more settings that are on by default and i hate those; but mostly those are subjective. However who wants 80px long "SIGN IN SO WE STORE YOUR BOOKMARKS, HISTORY IN OUR SERVERS" stuff on their screen?
I don't know, the other person responding also mentioned it scraping off all the AI crud, so I really don't think it's cryptic and I think everyone else knew that AI was one of the main "BS" features I was talking about. I am sorry I was not extremely blatantly clear enough for you. Feel free to move on if it is causing you this must stress.