Yes, some (all?) ask for DOB/age at sign-up. If I remember correctly, at one time Google even tried to enforce it and there were usability problems with typos

Yes, some (all?) ask for DOB/age at sign-up. If I remember correctly, at one time Google even tried to enforce it and there were usability problems with typos and wrong dates and things - there was no verification and no easy way to fix an error. IE, if a mid-40s adult accidentally entered 1/1/2024, they'd be locked out. And if a kid entered 1/1/1977, they'd have an account (but not way to correct that date when they eventually turned 18).