Yeah, the update just triggers one of my devices to turn off the encryption? Sounds a bit like a back door though.

It would only be a true backdoor I guess if they forced the update upon you.

Apple will prevent Apple IDs from working until you disable the feature (unspecified) probation period. They did a similar thing for older Apple devices where ADP was not supported but you used an account with it enabled. This can space time for users to delete their accounts or disable all cloud features should they want to.

There's no specific time on when it goes from being forced, but Apple is claiming to release documentation for off boarding UK users in the future. Currently UK users are saying their ADP is still on for now, but has an alert saying new users cannot enable it.