The reason is the rearview mirror cluster (for lack of a better word) the convience group has auto dimming headlights and automatic wipers which has the sensors by the rearview mirror. With both factory cameras, one is displayed in the rearview mirror and the other in the cluster.
Why on earth dodge didn't do them both on the nav screen heaven only knows. It could easily be selectable, or better yet a split screen would be slick with as large as the screen is. And while I'm dreaming, put higher resolution cameras and ones with a much lower lux (rating of how dark the camera can see)