That’s where I’m at. They could have just started doing this without even saying anything at all.
Read evidence from past trials it is obvious. See also successful and failed attempts to subpoena this info from VPN services.
Only people with iCloud will be using the relay.
It is true on the surface the photos is disconnected from the use. However, Apple only needs a solid answer that handles the bad optics of what you can do with the Tor-like anonymity of iCloud Privacy Relay.
However, if you look more closely, the CSAM service and its implementation are crafted exactly around the introduction of the relay.