And on the very few occasions I've had a vax card checked, they looked at it for 1-2 seconds and didn't check ID. It's a total waste of time.
The policy is in place to greatly decrease the number of unvaxxed individuals in the Joel, and it is obviously still working based on the question in this thread. Sure, somebody could fake a vax card, but what actually happens is that unvaxxed people just don't attend. And as you note, there is no inconvenience for vaxxed individuals - just 1-2 seconds of showing your card.