Because some games are designed to be precisely tuned to a very specific circumstance, and others aren’t. And I think that’s important to convey. Like, you can’t run anything but Night Witches with Night Witches. High specificity. But Dungeon World is specific insofar as it evokes the aesthetics of D&D but it’s otherwise pretty non-specific when it comes to its setting and premise. Or Hero or Primetime Adventures, obviously non specific.

Honestly all three can be trivially picked apart if you’re looking for this to be a theoretical structure.