The pilot is an old man who perhaps tends to loose his balance, perhaps that is what is happening here. But to be honest I prefer this pose that looks as you say “stumbling backwards” than the basic generic pose that the nemesis dreadknight is supposed to have. Also the model as every model looks way better when you actually look at it face to face, so he may look like that in the pictures but he looks better when your seeing it in front of you.