In practice, 100%. In theory we could likely design "good enough" anonymous systems that work like buying alcohol or tobacco in most countries (buy a scratch token in cash at a corner store after showing ID, picked at random from a box of them - contains a number, possession of which is theoretical proof that you had your ID verified at purchase)...but of course, the real purpose of age-gating is exerting a chilling effect, so we'll never hear about privacy-preserving methods.

(NB: I am firmly opposed to any of this. The solution for parents concerned about their kids is parenting and parental controls, not giving authoritarians of all stripes the means to snoop and ban whatever they decide is obscene or troubling.)

This approach could create a black market where,say, high school seniors would buy these tokens and resell to high school sophomores/juniors.