Had a scare when first hearing this. But somewhere else on the site it does specify this as something like “some physical games”, and as quoted in OP they’re contrasting here with “regular game cards”. So it appears real game cards will still be a thing.

So far I’ve seen screenshots of SFVI and Bravely Default boxarts marked as game-key cards.

I’ve seen box shots for Mario Kart and Donkey Kong that appear to be normal game cards.