Hmm, which seems more likely - Apple's decision to disallow multi-level folder hierarchies for their new integrated cloud service*:
(A) constitutes some sort of visionary forward-thinking insight into how the human brain processes information, or
(B) is because difficulties inherent in implementing automatic change-tracking and conflict resolution across arbitrary folder hierarchies on that scale (and for a user base with many non-technically-literate users) might otherwise have become an implementation and user/support nightmare, and they probably just didn't have enough time to get a solid working implementation ready for "version 1". ("You want it to do what by when!?")
I'm guessing it'll eventually be added in a subsequent version.
* It's not actually a "new filesystem".