UnityEngine.UI RectTransforms follow vastly different (and much more complicated) alignment rules compared to normal Unity Transforms that BoneFollower is designed to act on. I can't say when this will be done. But because of the fact, if it ever will, it'll probably be a different script/component.
It's probably easier/more immediate to handle just one case.
If you describe your specific need, I'll see if I can help you out.