I think you need to explain the solution you're thinking of in detail.
"an RFC that gives parents the ability to communicate their underage child is using the device without revealing or verifying any further information." is no different to "turn on age lock?" that you see on website now. It requires the parent to be present, engaged and 1 step ahead of their kids, and if we could depend on that, then we wouldn't even be having this discussion.
He was saying, vendors put that flag in the OS and parents set that flag in the OS and internet services respect that flag from the OS. No website anything, all in the OS. No staying ahead of anything, one and done. This, as noted above, requires that services respect the flag, which they do not universally do today. That requires legislation, something that will be a part of any workable solution.