I expected them to get rid of the 20th Century Fox logos entirely, for consistent branding with the other films. I’m honestly not sure why they didn’t.
This could be a GL thing, actually. He insisted that SW77 be preceded by the the fanfare even though it was falling into disuse at Fox at the time. In fact, it was SW’s popularity that led to Fox bringing back the logo+fanfare. So we have GL to thank for that!
I don’t think the short version of the Fox fanfare ever really went away. It was the Cinemascope extension that had fallen by the wayside, as Fox films weren’t being shot with Cinemascope lenses anymore at that point, although Rocky Horror did it’s own unique version of the longer fanfare even though it isn’t a scope film.