I think this article makes a pretty big leap in the middle. There’s really no reason that the operating system needs to be involved in the “Private” solution. It could just as easily be a website or a browser plugin. All you need is your government of choice to have some way to provide a token with whatever important bits necessary in it (“Yes this person is over 18 and a resident of WA”). You could even have third party sites/libraries that could read that token and verify what it contains.

The last third of the article is all based on that giant leap.

Or we could, y’know, stop trying to exclude young people from literally every possible expression or exploration of their own sexuality…