Just read through some COPPA stuff. It looks like you could comply with a simple checkbox for "I am over <magic age>", which would be less information for the panopticon.
I'm no lawyer and can't say whether Google complied in a minimal fashion or not. But maybe not. [Edit: Checkboxes are insufficient, apparently]
Their implementation has to comply with laws in other countries too. Plenty of countries consider a checkbox too easy to accidentally tick, whereas asking for DOB requires a user to actively make up information, committing fraud if the information is false.
It might be fraud for a child to give a false birthday to get access to an adult service (or vice versa) but it's not fraud merely to give a bogus birthday.
Also, you know, since Google knows the account age and all other information about the user it should be able to give an educated guess about the users age
But apparently Google's knowing that you're a right-handed tae-kwon-do enthusiast that flies every month is not sufficient for them to maybe think you're not a minor.
Google runs the play store. The play store requires a credit card. No one under the COPPA age can legally own a credit card. We should have been done there. And if we're talking purely gmail, a binding "please confirm you are over <age>. Note: this is a legally binding answer and Google reserves the right to delete your account if provided with incorrect information" should be more than enough. Google does not need a full date of birth. But boy howdy do they want it for advertisement purposes.
The Play Store doesn't require a credit card, at least not in the U.S. I have a Google account that I use for testing on an Pixel phone. When I go to install a new (free) app, it nags me to add a payment method to my account. But I can skip the prompt and download the app.
if you've never bought an app on the App store, you're not really using your modern pocket computer to its fullest. Most of the good apps, and good games, cost money.
Nonsense, "you must be at least 13 years old to use this service" has been standard T&C since time immemorial. It is not a basic piece of information either, it's a big piece of identity theft. So not that I'd even give any online service my real DoB anyway.
I'm no lawyer and can't say whether Google complied in a minimal fashion or not. But maybe not. [Edit: Checkboxes are insufficient, apparently]