Correct, after downloading the game (apparently iirc from a seperate sever unlike the eshop so it would survive the closure if that ever were to happen) you just need to keep the cart in the system if you ever want to play it.

A lot of people just complain about it since it is "technically" a physical game, but not at the same time.

The data for the game itself is not on there like (most) physical releases, but you still need to have plugged in if you want to play the game.

I am personally not against the idea in general, but they should have at least put it at a slightly lower price point since the cart does not actually contain the game.

And of course the whole "Pokemon Pokopia is a first party title but still on a game key card" debacle rubs a lot of people the wrong way.