If I recall correctly (always a question...), TBB mentions that rawhide can either pull a bow into mild reflex or hold it there. I think they mentioned you needed to use real hide glue or some such thing to allow the contraction, as opposed to TB, as it functions a little differently and does not permit the contraction while drying as hide glue does.
But, I could be way off. Either way, it's a great backing material.