Unless JCE changed them around, there's a bit any formation can use which apparently only the Floating Continent originally did. It's called "random with next 3" which for lack of a better explanation, if this bit is set for a formation, the game will use the RNG and randomly add between 0-3 to that formation number, giving a possibility of 4 different formations that can appear for one. This can be used to greatly diversify an area's monsters if you don't mind using up the formations.
