This law doesn't do anything that prevents non-anonymous access. Here's how you would access things anonymously if you bought a new computer that implemented this.
1. When you set up your account and it asks for your birthdate, make up any date you want that is at least far enough in the past to indicate an age older that what any site you might use that checks age requires.
2. Access things the way you've always done. All that has changed is that things that care about age checks find out you claim to be old enough.
The only people it actually materially affects on your new computer are people who cannot set up their own accounts, such as children if you have set up permissions so they have to get you to make their accounts.
Then if you want you can enter a birthdate that gives an age that says non-adult, so sites that check age will block them.
From a privacy and anonymity perspective this is essentially equivalent to sites that ask "Are you 18+?" and let you in if you click "yes" and block you if you click "no". It is just doing the asking locally and caching the result.
I agree. I feel the flow of having browsers send some flag to sites is the most privacy-preserving approach to this whole topic. The system owner creates a “child” account that has the flag set by the OS and prevents the execution of unsanctioned software.
This puts the responsibility back on parents to do the bare minimum required in moderating their child’s activities.
I'm not sure it's worth entertaining these hypotheticals. Just another absurd CA law that's impossible to comply with. "When you set up your account and it asks for your birthdate." What does this mean? "Setup" what account? "It" what? Some graphical installer? What if I don't want to use one? How would this protocol be implemented in such a way where it's not trivially easy for the user to alter the "age signal" before sending a request? The "signal" is signed with some secret that you attest to but can't write? So it's in some enclave? What if my smart toaster doesn't have an enclave? Does my toaster now have to implement software enclave? I'm not aware of a standard, or industry standards body, or standard specification, or implementation of a specification, around this "age signal" thing. Is this some proprietary technology that some company has a patent on, and they've been lobbying for their patent to be legally mandated? If so that's very concerning and probably has antitrust implications (it is ironic that ever-tightening surveillance of people is a downstream consequence of all this deregulation of corporate persons; fine for me but not for thee I guess). I would love to know the full story here, since this is being shopped around in several states, but I haven't seen any sort of investigative journalism about this which is disappointing. This whole thing is really curious.