Why doesn't Jaw surgery widen the ramus? Is this possible via osteotomy? Widening only occurs in some cases.

So I was looking at jaw surgery (orthographic) surgery results for those who have recessed jaws like me. When I look at the front view I see that jaw surgery typically does nothing in that regard. Why does it not widen the ramus? Is the square jaw look simply the width of the jaw? I also notice widening of the jaw only occurs in some cases of BSSO. Why is this?