Well not really, they added a field so that they could store date of birth in the way they have a field to store "real name".

So you can be sure my birthday is 4/20/1969 as sure as you can be that my name is Bimbo Baggins.

Note that for the California law at least, this is "good enough" and the OS never actually has to validate anything. In practice a person without admin access could have their birthdate out of control, well, until they run a patched browser that skips asking systemd and just always sends a desired bracket...

It kind of works to keep kids under 13 sending the signal with parental administration, but doesn't do anything for more resourceful people you tend to find over 13.