Just going to put that here: "implementing are verification" is misleading, other distros are just using vanilla systemd that has a added a field for birthdate, which not only you don't have to fill but also there's no UI to fill it now.
Ofc some of these distros will end up complying, but it'll probably be opt-in & let you decided whether or not you want to fill it, and/or enforce it only in specific region.
Real enforcement won't happen at the OS level but at the website level, where websites will lock you out if you don't have the age AND are in a legislated region.
Anyway it's just too early to know which distro will do what, and using systemd is not a relevant signal these distro will mess with you for the time being...