Game-key cards are different from regular game cards, because they don’t contain the full game data. Instead, the game-key card is your “key” to downloading the full game to your system via the internet.
Pay a premium for a physical copy of your game, and the cartridge may not contain the actual game. Only on Nintendo Switch 2.
Nintendo’s site says the cartridge must always be inserted in order to play the game, and so it is the cartridge that controls the game license.
On that basis it seems likely you could sell/give the cartridge to someone else, after which they can play it and you no longer can - they’d just also have to download it first.
Until the download servers go down and you have a cartridge that’s just ewaste
Yes, which is a big part of why, despite allowing transfers, it still sucks.