They also can't refuse to comply with warrants demanding any such unencrypted data that is stored on their servers.
That's not the same thing as adding a back door to allow access to encrypted user data that is stored on the user's device.
It's also different than storing encrypted user data on your server, when you have purposefully designed a system where you don't have access to the user's encryption key.
Encrypted user data backup is the feature that Apple disabled access to in the UK rather than comply with the order to insert a back door in the OS.
I would also point out that it was Senator Wyden who initially informed the public of how much the government was already spying on their unencrypted communications.
His record on civil liberties is excellent.
Good security models typically don't hinge on being lucky.
Should we disbelieve them when they say they don't do so?