I'm playing as the purple Ewoks Miwot and have noticed my nearest neighbors, The Navigators, have decided that far too many of their worlds should be Core Worlds. Even a Class 11 world—Diadem II—that's surrounded by other Navigator Core Worlds, as seen in the screenshot below.
This is diluting the AI's military production, which essentially means I can rush-colonize several star systems while they struggle to build even a single Tiny ship.