The Patreon plugin works fine for pages but I don’t use it for age verification. I don’t know how I could do that. The age verification is done manually by me. Unless you are added to the verified group, you can’t see the age-restricted content. Essentially the two systems are pretty much separate.
Patreon only allows restricting by Patreon level (ie fee paid). I don’t think they know your age or give me access to that data (which they probably don’t have themselves). I’ve never been aged-checked by Patreon.