But that's not something with only approved microSD cards work with save games. The Switch will not write save game data to any microSD card, regardless of features/manufacturer/branding/royalty payments/whatever. It's just not a supported feature, at all.

The GGP comment makes it sound like Nintendo only supported proprietary microSD cards at launch. While they did sell and recommend their branded microSD cards, one could use any brand of microSD card with the system and have the same functionality.