[Does this truly happen often among multi-armed recurring bosses? I mean, how often do you even see multi-armed recurring bosses?]

Well, we are foreigners to this world. Would you allow Fabul or Eblan to suddenly take control of Baron? As for soldiers, there doesn't seem to to be any sort of demand without war and the Pokémon being mostly peaceful, and there isn't magic here, so mages would be useless. We hardly have the skill sets that this place could use.