Posing is a communication tool for throwing discs to dogs (or people). A pose is a frozen moment of a throw; a key moment of the backswing perhaps, or a flashy presentation of the finish of the throw. This pose cues the dog in on which throw is being made and delivers a general sense of where it is going.
A pose communicates many things: direction of throw, type of throw, spin, and location, but it can’t communicate any of that if the dog doesn’t see it. Perhaps the most important part of the pose is the dog’s participation in the throw. Looking at the pose makes the throw happen and the catch likely. The dog understands that looking at the handler triggers a very catchable throw.