Whether it should be government-mandated is one question,

That:s my primary issue

That's my issue too. We're in agreement, but I just wanted to point out that the "it's the parent's job, not the OS's" doesn't communicate that and instead applies a blanket statement that actually undermines what you're saying you want.

The other guy is right when they say it applies to the check existing on the web-level. That is the issue, in my opinion, and I think people are just conflating that issue with the OS value's merit. Having a check at web level is actually what removes the responsibility and capability for parents to parent their children. Having it at the OS level makes it a tool for parents to use. They don't have to set it up, but the idea is that it makes it really easy for parents with zero computer prowess.

Again, should it be government mandated on the OS side? I strongly don't think so. But if anyone has a good solution to not mandate developers to respect the browser's report of the parental controls setting, I'd love to hear it (zero sarcasm, I don't want to have anyone breathing down my neck to implement this stuff either). The best I can think of is to take advantage of AI, but I can see why it could be unsavory. Should the browser itself carry a database of sites it has scanned and then use that to determine whether a site is safe? Should it query a user-owned model that's more customizable for the parent's tastes? Can we get that to run locally for everyone?