The concern is if you lose your devices with E2EE enabled then you are locked out permanently. Grandma won't know how to use a Yubikey (which is the alternative Apple provides for this eventuality with ADP enabled) and will be out of luck.
This is not a requirement with Google's solution. After losing all your devices you only need your lock screen code to decrypt your backup, as I said. This is achieved using a secure element on the datacenter side to protect against brute-force attacks on the screen lock code.