I'm also not sure (like Larinda) about your question; my answer would be that these alignments are for usual situation when the couple is dancing along LOD (which of course isn't exactly straight line in most parts of the room, because dimensions of the room are limited)
even concur about some basics of movement.
Suppose 12 o'clock is FW (forward along wall), 6 is BW (back along
wall), 7:30 is BDC, 9 is C, 10:30 is DC, etc... You mention that
you would end count 6 roughly with both feet pointed DC (10:30)
and this would probably correspond to some (horizontal) location X
past halfway along the wall. Say you travel some 4 feet on the
ensuing 123 and end up at location Y on count 3. At what clock
position (angle) would Y be with respect to X (remember your
feet are pointed at 10:30)?
Note that I'm purposely avoiding the use of "LOD" as it isn't
meaningful due to the changing angles.