Further, on "if you can hit, you can be hit": No doubt. However, I think the significance of the strike isn't to do damage (of course, catching a choice point with even a light strike would be nice) but redirect attention momentarily. Further, by getting the hand in between there, seems like it would give you a shield against uke's left for a brief moment.
This is not necessarily true. If you control uke's hips and center you can hit him, but he will not be able to hit you effectively.