In the video Kent says it’s to separately influence the bottom part of the droplet, and the other bone that stands upright is for the wiggling. So basically just to have those two functions separated, have the base not move at all and delegate the wiggle to the upper part and control it freely. That’s how you get a droplet to move to the rhythm of the Macarena.
Though he doesn’t use it that much. The base one could also serve as an overall translation bone, if you want to move the droplet to another position.
