alt Hacker NewsSo basically parents set the child's age and apps rely on that if they need to know if the user is old enough?
That's pretty similar to the California bill. Parents set an age when creating a child's account. The OS provides an API to get the user's age bracket from that, which apps that need to know the age bracket of the user can call.
The California bill gets it backwards. Rather than Internet services taking the user's age and deciding what content to serve, the Internet service or app should broadcast the age rating of its content to the OS (if convenience is desired), like how movie ratings work. The responsibility to decide what content is suitable for a child should rest in the hands of that child's parent, not the state or the corporation.
edit: on second thought, realistically, the API solution is too brittle regardless of which way it goes. Because the API requires every service to implement it and that's not happening, whereas an app installation lock only requires one child-friendly OS to implement it, then parents can choose that OS.