I agree there are reasons to be concerned overall, but Tim Cook is very clearly stating in this interview, which happened after the nationalization, that 1) China doesn’t have access to the encryption keys themselves and 2) for much of the data (like messages) not even Apple has the keys, 3) China is not able to access the data any more easily than any other country.

If you are targeted by the CCP, then yes, they can make a “legal” request for the data of an individual that Apple is able the decrypt (which isn’t all of it), but they aren’t able to apply mass surveillance to the iCloud data.