I think you may be misunderstanding a bit. There's no forced verification. It'd be more of an RFC that gives parents the ability to communicate their underage child is using the device without revealing or verifying any further information. Or do you suspect that giving any ground will cause the ID verification and centralized behavior?
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.
I suspect that communicating a flag value of boolean true/false that "this computer is in use by a minor" from the operating system (via browser or app) to a remote SaaS service like something run by Anthropic will be seen as insufficient by the SaaS, so they'll necessitate ID-scan/live-selfie verification anyways.
Meanwhile, the age flag in the operating system will be used for other forms of authoritarian control. It will have actually accomplished nothing other than limiting peoples' fundamental civil liberties.
I think the concern is a forced bit of functionality in all operating systems. It would quickly lead to a "and you need a license to sell your device so we can check that it can't bypass mandatory chuld-safety guards". Just like how some politicians are proposing mandatory licensing for releasing any AI model.