So this is where devils advocate comes into play. Pretty sure we all are agreed that this law, or anything like it, is 'not good'. And I'll leave it at that. Just keep that context in mind as I elaborate further.
Windows actually does do this on install. However, the Microsoft Family feature uses Microsoft Accounts. So technically, sure it's not the OS (though it IS part of the OS, as you don't need to download anything extra to enable it's functions).
But you have to go out of your way now to do an offline windows install without a Microsoft Account. If you're that savvy, you're capable of monitoring your child without the help of big government. If you're a child, then nothing but honesty is keeping you from jumping walls.
But that is windows, and this is Linux. Now I'm not making accusations, but do we really want to push the idea that this form of control needs to be pushed out across everything, simply because the current solution that would work for most families isn't done at the "OS" level?
And to top it off, I don't even see it working. Most family devices are set up on an account with a single login. Managing access is not a 'one and done' process, at some point you will have to provide permissions, install software, change active hours, approve screen time requests, troubleshoot related problems, and more (and soooo much more if your kid is technically adept). Is it no wonder that most parents just give kids free reign to their computers and consoles?
So before we go around and ruin the experience and privacy of everyone, can we at least ask what the people who want this have done instead? Cause it really does feel like it's coming from a group who wants everything done for them.
Fair on the privacy aspect, but again, I'll point out that Microsoft Family already does the age bracket thing. I think how it's done is slightly different, as software/websites have to disclose age groups rather than requesting it. Different sides of the same coin to be sure.
As for parents, I think it's a mixed bag. I know a lot who are a mess at computers. Most don't even know these tools even exist. Those that do, don't have the time to do it properly (it only takes one night when your kid gets locked out of their account doing schoolwork due to screen time limits and your trying to troubleshoot why your approval to your kids request isn't going thru via your phone, etc). But there certainly are also those that don't care at all or feel they shouldn't have to do it. It's getting better though, I see a lot less young people with tech blindness every year.