Chief Chook.... so does QF.
The -400 is a special case because of the requirement for SO's AFTER SIN on the way up to Europe. So they operate instead of filling a P or J class seat. In fact QF does THAT leg cheaper than SQ, having a crew of one Captain, one F/O and two S/O's instead of two Captains and two F/O's...
You still want Geoffrey listening?