Maybe there hinting that they might put it in KH3 or something? I mean they don't leave things like this in a game without having a reason for it being in there.
Yeah, to keep the game running right. Removing data like that can make the game unstable and makes more problems trying to debug it than just leaving it in.
It just shows that they had been thinking about a JB world but it got cut eventually. We could get it in later games though. Hopefully. I can see Sora in JB more than Terra or Aqua.