My Call History and Block List Came Back! Why?

Recently we've seen that the iPhone call history and block list comes back after setting up an iPhone as new and signing in to iCloud. This is a feature of iOS/macOS Continuity. Your block list and call history are stored as part of Messages, Facetime, and Phone handoff in your iCloud account, so after setting up an iPhone as new, and logging in to iCloud, your recent call history and block list repopulates from iCloud.

This will happen if you're using a cleaned Decipher Phone Refresh/Decipher Activity Transfer backup. It will even happen if you set the iPhone up from scratch restoring no backup whatsoever! So here are a few notes and tips:

• If you are using Decipher Phone Refresh or Decipher Activity Transfer to address an issue with a broken call history database, this still works! Your old call history database is no longer part of the backup, so the Phone app has to set up a fresh database. Your corrupted call history should still be fixed, and then the new entries from your iCloud account will be populated into a fresh database.
• If you need to erase a large number of blocked numbers, and you have access to a Mac (macOS El Capitan, Sierra, and higher) open the Messages app and go into Preferences. In your iCloud account preferences, you can access the block list and delete the contacts by pressing the delete key, rather than swipe & tap on your iPhone or iPad.