In my play against the diagram, I did come across a different situation in which one might want to promote an Elephant to a King instead of a Saint or Ghost. This occurs when one wants to deny the opponent the opportunity to get the Saint or Ghost by re-capturing. The diagram used this ability of the Elephant to prevent me from getting a Saint, and that actually saved it from almost certain defeat, though I doubt the diagram would have let that situation arise if Elephants didn't have this ability. Still, I completely didn't see it coming and went on to lose the game.
In my play against the diagram, I did come across a different situation in which one might want to promote an Elephant to a King instead of a Saint or Ghost. This occurs when one wants to deny the opponent the opportunity to get the Saint or Ghost by re-capturing. The diagram used this ability of the Elephant to prevent me from getting a Saint, and that actually saved it from almost certain defeat, though I doubt the diagram would have let that situation arise if Elephants didn't have this ability. Still, I completely didn't see it coming and went on to lose the game.