Apple has found itself in another privacy related controversy, this time over a decision apparently made two years ago, but only coming to light now. According to Reuters, Apple abandoned plans to fully encrypt iPhone (and iPad) back ups in iCloud following pressure from the FBI. The move raises serious privacy concerns for a company that touts itself as a user privacy leader.
https://www.notebookcheck.net/FBI-pressure-leaves-iCloud-iPhone-users-vulnerable-to-unencrypted-back-door.451018.0.html
From what I've read, it doesn't constitute a "back door" as you've alleged. Apple has the encryption/decryption keys for those mentioned services, but does not hand over said keys to authorities, and instead decrypt the data themselves and hand over the information to the asking party.
Also, none of this is new. Apple already clearly states what services are end-to-end encrypted and what services are only encrypted on-site. They'd have a web page that lists all of it for a number of years (iirc, ever since Appe Health debuted).