I have a weird feeling that this photo is deceiving... his weight is obviously on his front foot, which would make a forward movement fairly powerless - not typical of O Sensei at all.
I think he is actually pushing off his front foot, dropping back and bouncing uke into the hole that his body is leaving. That would make the head position seem very natural...
We are about 60% weighted on the front foot at that point, but our posture is erect and our throwing arm is stiff and angled sharply downward. Uke is falling distinctly downward, moreso than forward. Kind of like Saito Sensei is doing here, but shite is more upright, so uke's back is more parallell to the floor: http://members.aikidojournal.com/wp-...nage-2-uke.jpg