You have overlooked that the system for protecting minors from sexual messaging /is/ the parental controls you wish it was, and is /not/ the serious privacy invasion you think it is. It is on-device only, it only alerts the parents, in the condition that the parents enable it and the child continues past a warning informing them that their parent will find out if they continue.

> "The parent can be the admin of the child's devices, and have access to their otherwise encrypted messages."

Apple have done even better - the parent doesn't get access to all their messages (at least not as part of this system).

This is not the same system as the photo-scanning and authority-alerting one.