Age verification and stored date of birth

The age verification FAQ says:
“VRChat requires your birth date to ensure compliance with our Terms of Service”

I understand why this is the case so long as age hasn’t been verified. However, if someone verifies that they’re 18+, why is retaining the date of birth then required?

Surely, if you can produce a hash confirming that the user is 18+, that then confirms they are complying with the ToS, and the actual date of birth is no longer required?

It seems to me that if you’re storing the minimum necessary PII about your users to carry out this function, then it should be possible for anyone who has confirmed they are 18+ to remove their DOB from your system while retaining that verification.

If the age-verified user is under 18 you could store the date that they turn 18, and on that date replace it with a flag that they are now over 18.

A date of birth is much more personally identifying than a yes/no 18+ flag is. I’d be much more inclined to verify my DOB if an additional benefit was that you could then hold one fewer piece of PII about me.

While you’re not going to like the answer I imagine they’re doing it for analytics reasons. It’s a lot easier to get points across in a business environment if you can say “VRChat on PC is popular with 20 to 32-year-olds” instead of “VRChat on PC is primarily used by an 18+ userbase.” While we as users of the platform understand the proper subcontext, someone outside of the platform might make assumptions if VRC lacked granular age data.

Again this is all speculation on my part so I could be completely wrong about all of this.