Hi there,
Really appreciate the feedback, to answer your questions;
-Indeed, there was a new room added there but we removed it as it was redudant.
-This actually duplicates a mystic quest behaviour, so this was intended.
-You can reach this chest from the Kaidge Temple later on in the game with use of the Mobius and Gemini Crests. This is for a secret side quest :)
-It sounds like it's bugged, which I'll fix :)
Kind Regards,
Jake