Maybe it's me, but if I set a start and/or end shape, the shape the line starts with is the end shape and as I draw the line, the shape under my cursor is the start shape. I would think it should logically be the other way around. No?
Yes, it would make more sense to be the other way around (with start being the first clicked position), however, initially line layers could not be added by clicking, only by dragging, so "Start" position was made the one at the 0 deg. point.
Unfortunately we cannot change this now without breaking existing functionality for users.