Sorry, deleted my last response, because I noticed that this is using bendy bones. To answer your quest yes you can use the out bone, but you have to kill it’s parent or parent it to the root bone. It can’t be parented to the def bone. The other side effect will be that the top bones axis is not aligned to the world axis. This makes animating a little more difficult. Also it’s common to separate Deformation, mechanic, and control bones. In this case the in and out bones are mechanic bones. Blender treats all bones the same, but some software treat them differently. So, Riggers get in the habit of separating them.
