This type of system is a horrible idea for the following reasons:
1) the cards can just be re-sold which creates a black market and defeats the "cashier physically saw the person buying the card" angle
2) nickle and dimes people for simply browsing the internet (verification can dystopia anyone?)
3) related to #2, it creates winners in the private sector since presumably you need central authorities handing out these codes
I abhor the idea of digital ID verification, but if we're going to do it, let's not create a web of new problems while we're at it.
First - Alcohol and cigarettes can just be resold too. The black market for them is effectively zero because the consequences for giving them to kids are severe and the room for meaningful profit is close to zero, same applies here.
Second - The codes would be priced on the order of magnitude of pennies per verification - think 10 cents or less, accessible even to low / fixed income folks without really making a dent in their budget.
Third - the proposal explicitly mentions a nonprofit running it as an option, and the idea would be that law codifies the method to be approved, not a specific vendor, so competitive markets could emerge, too. Would you argue that restrictions on the sale of alcohol are creating artificial winners in the private sector of alcohol manufacturing?
Is it even theoretically possible to have bearer anonymity and no reselling option at the same time?