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.
Not only on Switch 2. There was at least one Tony Hawk Pro Skater game that did this.
If I remember the episode of Guru Larry, the developer noticed their rights to the IP were set to expire, so they went to shit out one last game as fast as possible. They had to get the game published by a certain date, as in discs on store shelves by this date. The game was not going to be ready in time, so they put the tutorial level on the disc to print and distribute it while they finished the game, which would then be a multi-gigabyte download. Meaning that a physical copy of the game is worthless once the servers shut down.