In my Hapkido school we have a long sword form that does exactly that block behind the back as part of it, and then a further unwind to a high block. Great fun to do when you get it right. As the name suggests, it's design for a long sword - straight-bladed katana approx 4.5-5 feet in length. I also practice a twin sword pattern from the Muye dobo tangji that contains 3 sword spins with both swords. The final one starts with the swords in normal grip and ends up with both in a reverse grip (blade of the sword back along the arm, hilt away from the body), stabbing behind you. Tricky to get right, but once you do, it looks great