"If you were having an examination to become a teacher and on a Spin Turn you said for the man step four does not go straight back down the LOD. You might fail. And yet we all know that step four for the man goes diag to wall."
Your argument is based on a flawed premise.
For most dancers, the thickness of the body from front to back is on the order of half its width from side to side. This means that the space occupied by one body square to the LOD is also sufficient for two bodies sideways to it. We do not detour out of our partner's way, we move through the same space that they previously occupied, or at times sharing the space with them by both feathering our bodies relative to the direction of movement - the two fitting sideways through the space one occupied square.
The reality is that the backwards CBM step needs to curve very slightly to one side of the original body outline, but it really doesn't need to go off to the side. And it's important that it makes its slight curve in a way that keeps the thighs tending together. Separating the thighs into an actual sidestep, or getting the trend of the movement going off towards the wall rather than flowing down the LOD would cause an ugly lack of coordination with the forward partner who must move directly down the LOD. A frequent problem even in world finals, unfortunatley.
