This is not on iPhone but on a MBP so it's still quite relevant to Apple. I had disabled the "apsd" process, which serves as Apple's push notifications service, completely blocked it off using Little Snitch, and yet the process still found its own way to reactivate itself and keeping a persistent connection back to Apple servers in the background. I personally don't use FaceTime or Notifications on MBP, why couldn't Apple just let me disable this, and instead the process even circumvented around my firewall protection to make sure it could communicate back to their data center? This practice is a little shady and does not promote trust or transparency. If I have blocked a process permanently then I expect it to remain always blocked.
Their EmbeddedOS on the Touch Bar also keeps a couple always-on connections that utilize its own bridged network interface which users are completely blocked off and do not have access to. They were supposedly for TouchID, but I was viewing bandwidth usage the other day and these connections used up to almost 10MB of data. Why would something like TouchID need to send 10MB of data back to Apple? Again, this makes no sense and does not promote trust.