S&W's that I have seen, can have from 4 to 12 pieces (and sets of repeats in them,) and there are many different block choices, where OBW's only have 6 are are hexagons only (or cube shapes) :D:D:D
These blocks/quilts are defined by the technique of stacking your fabrics in the manner shown above, and cutting out shapes so each piece is identical in shape, and also the placement of the fabrics details on each piece, to make a Kaleidoscope effect. :D:D:D
I have a OBW planned that will use several colorways of the same fabric... it isn't a hard and fast rule to use only one fabric, it is up to the quilter :wink:
One S&W quilt was made of blocks with 12 fanblades (12 repeats) it was gorgeous :D:D:D