Grandpa isn't interested in Discord, so you can open a second account using his Proof of Age. Maybe a third account, using Uncle Ned's. And a fourth account, using...
I'm not defending age verification's existence in the first place btw, I don't think it's a good idea without secure protocols of central attestation for such things. But of course, governments aren't interested in solving the harder more valuable problem, they're interested in shifting the responsibility to corporations while crying foul.