still though it just feels out of place to have one new world out of a bunch of old ones
Not really. Monstro was in the first Kingdom Hearts and we never saw anything about Pinocchio after that other than in CoM, which was just a memory.
From what we've seen, it's pretty obvious that Nomura wants to expand on the KH1 worlds. We're obviously not going to go to Monstro again, so Pinocchio's world is where we would go instead. Besides, wouldn't Nomura want people to actually visit Jiminy's world since he appears in KH so often? The only real boss you could get out of a world like that would be a Heartless, and this is the best time.