For those interested on the question of age verification and GNU/Linux: be aware that Systemd v261-rc1 was recently released. It now implements an optional birth date field in the JSON user database (see second item under “Other changes”).
The implementation of this field was prompted by age-verification or -attestation laws.
Yeah just because they build cages for kids in the desert near the border doesn’t mean anything’s going to happen! It’s just optional infrastructure in case you want to put your kids in a cage. It’s totally voluntary.
There are genuinely useful use cases for it, and unlike what you suggest it is completely harmless.