@[email protected] @[email protected] I think in both cases there's also a practicality aspect: having taught tech skills to primary school children I can tell you that a sizeable percentage (verging on a majority) have at least some access to devices where they are logged in as one of their parents to at least some services. More than 10% so far have devices they carry with them that are logged into a parents email account, meaning they can (if they know how) reset the password on most online services and then delete the evidence of having done so.
Assuming my experience isn't unusual, and I have no reason to believe it is, I cannot see any way to target restrictions by age that isn't nonsense; a sizeable proportion of children are browsing the internet with completely legitimate 'adult' accounts out of a combination of convenience and lack of knowledge already.