I think you are confusing several different aspects of security and privacy here, like iCloud data backups and encrypted local iPhone storage. Apple does have access to iCloud data, but they do not and cannot have access to locally encrypted stuff which is locked behind your personal PIN code. Apple does share iCloud data with law enforcement.

Knowing this allows users to improve their protection and privacy at the cost of convenience. For instance, one can avoid using iCloud altogether, or choose to encrypt iCloud backups.