LD_PRELOAD can intercept getpwnam(). Why not getpwage() as well?

Yeah if you have admin access to your device and know what you’re doing it’s basically a non-issue. I’m guessing a savvy high schooler can change their age bracket easily.

If you want to give a young child a laptop or computer though, it maybe helps keep them away from objectionable content.

The California law says nothing about verification or immutability, what if someone made a mistake when putting in their age? Why do we need to hide it? Better to just let the user change this at will.

Yeah the most likely thing (for the California law, at least) is that compliant OS's expose a form at account creation where you input a birthdate or age, and have either a CLI/file/setting where you can change the birthdate or age with admin permissions. No verification is needed