If I were building the feature, I'd put the "adult" header behind a password.
But that's a solution only for the one browser. You'd need to forbid the OS account in use from installing new apps so the kid can't get a different browser. And now it's starting to be inconvenient for the parent.
Trump and his supporters have Congress by the short and curlies, unfortunately.
You mean this?
https://threadreaderapp.com/thread/1855616243039916152.html
That doesn't fit your description.
There's a somewhat antiquated idea of honor that accounts for that. A good man can definitely be on the other side, and you need to kill him anyway.
The vast majority of kids would be stopped by the OS account restriction, especially now that they're growing up with iPhones instead of Commodore 64s.