Websites should have an easy way to check whether the connecting device has a child lock turned on. We don’t need to identify the person using the device at all. It should be up to parents to make sure their kids use device that are locked.
This is clearly the right way to do things. Just make devices have a forced choice for their age setting on initial setup, and expose that to apps and websites.
Insane that they didn't even try this simple solution first. Yeah people will get around it, but they'll get around any solution.
Or even better, just let the website return a set of flags (like age_rating=18) in a header and let the user agent decide if it wants to show it, block it, ask for approval, ...
Then the policy lives on the user agent.