Apple uses different encryption for different data, most data like contacts and mails are NOT encrypted end-to-end:
Although some like Messages are encrypted end-to-end, the private key for that end-to-end encryption is backed up on iCloud Backup - invalidating the whole point of end-to-end backup.
Use of biometrics (e.g. Face ID, Touch ID) to provide access to end-to-end encryption is also problematic:
- They are difficult if not impossible to change if stolen.
- They can be obtain quickly by force - pushing you hand on to your phone or face in front of your phone.