As I said, pre-CAPS animated features were clearly shot with a lot of "breathing room" so they could be presented matted anywhere from 1.66:1-1.85:1. The 4x3 releases may be slightly cropped because showing the extra side information visible in the widescreen transfers would also reveal unwanted vertical info, like cels that end within the frame - "floating torsos", etc.

Jungle Book wasn't theatrically exhibited in 4:3, so both ratios are valid. But I do like the idea of showing as much of the exposed frame as possible - there are a few 90s animated films (not Disney) where the widescreen and 4:3 versions each show unique picture info, indicating that they were shot at something like 1.66:1, and there is part of the frame that's never been seen in any transfers.

But that's probably not going to happen any time soon...