I'd bet that the head turns are controlled by the roll axis. Take a look at the last picture. Ailerons are showing he's about to roll to the right and his head is pointed to the right.
Edit: In fact look at the last Sopwith Camel picture, same thing.
Edit2: Also since you can't see control surface movement in the film viewer(I think?), we know these are in-game shots. So he has to be taking these pictures from the external view where he can't be changing his internal head position.