I think it's simple. If your race/gender combination didn't have a hands-on-hip pose, you got one now. If you already did, and it was too similar to the one others got, you get a new pose that is one hand on hip, the other dangling. Thus, for example, I imagine midlander women will get hands on hips for a pose, while highlander women (who already have one) get one hand on hip and the other dangling.