Another possible interpretation... you don't see a sniper: you cannot look directly at the Sun.

A pourer in modern times is a little spout you attach to a bottle of spirits, so you can more easily control what is pouring. I have no idea if they had something similar in ancient Greece, but pouring (in general) seems to be more controlled than dumping. And the Moon reflects *some* of the Sun's light, but only some, so you can look directly at the Moon.