This begs the question, if Vegapunk did nonetheless build in some switch or overriding command into Kuma without saturn noticing... . Because we can only assume that Kuma could have reacted on Shaka's command to prepare for battle, shortly before he activated himself. But maybe that was coinicdental.
What interests me the most is, what Kuma will do after he arrives, where he is currently heading (I assume this must be Egghead.). I wonder who will have the highest command then: Saturn or Vegapunk. Or maybe Kuma can to an extend really decide on his own and did fly to where he wants to fly because he decided that for himself... .