“When it detects a user may be under 18, Google will notify them that it has changed some of their settings and will offer information about how users can verify their age with a selfie, credit card, or government ID.”

Selfies are useless as proof for young adults and people with a young face. No algorithm can tell a 17.11 yo from a 18 yo so it will flag every single one of them.

This is a way to normalize handing over your details for the next generations