The diagram does show when the fan is blowing down,the air is directed outward from the stove,which is necessary to push air from the stove room into adjacent rooms. Blowing up would have a minimal effect on adjacent rooms as the air goes down the walls and back toward the stove.Here's a nice illustration showing the difference between up and down.
ttp://www.hearth.com/talk/attachments/ceiling-fans_h-jpg.81051/
Of course, it's going to be a matter of what works best for you . Fortunately, it's easy to experiment with...