I might have gotten things messed up because I am not a medical student. Apparently the swap happens only for MRI and similar things where the picture swaps the coronal plane.
If you want the explanation for it search for sagittal and coronal plane. It gives you a way of talking about bodies independent of rotation.
Have you talked to 17 year olds? They are far from developed in most cases. Anyone even in their late 20s should notice the difference in development and stay clear.