The age verification API in operating systems is a really good idea for privacy and parental control, so long as it doesn’t require literally collecting your ID (it doesn’t).
Look at it from the perspective of a parent giving a device to a kid. Before, you’d have to deal with a maze of blocking content. You’d have to allow/blocklist a huge number of apps and services manually. If your kid discovers some new one you or your blocking service has never heard of, they’ve gotten around your parental control wishes.
With the age verification API, you just set the age in the OS (and lock it down with MDM or whatever) and now all the apps and websites have to respect it and act accordingly.
Your kid can’t just make a new account or download another browser or do some other crazy workaround to get around your restrictions. That setting is there at the OS level.