If it was possible to reliably verify your age with other body parts would this be implemented?

Age gating has become a big deal over the last few months with Australia implementing it for social media and other countries discussing it.

Some people suspect it is being used for government or even corporate surveillance as it'll become very difficult to do things online without paying with a credit card or showing your face. I'm unsure what to think.

A solution to this is simply to use a body part that reliably changes with age but doesn't exist in public databases. A reproductive organ probably wouldn't be acceptable but maybe a hand. A small part of your face. Teeth. Hell even buying a gift card from a store.

The body part is not the point. Would a method of verifying your age that did not exposre your identity be accepted? I feel like this would confirm the motives of age gating.

So if this was possible, would it be implemented or not?