Well . . . you're not going to cross-fire with a pump or auto, for sure. But does that guarantee the gun shoots where you aim it? If we assume that the barrel is perfectly straight on a pump, auto, or single barrel, then why do we bother checking where a rifle shoots? After all, the spread of a shotgun pattern is going to compensate for some degree of impact error. In other words, while you may miss (or just chip) a target or a bird you should have hit had it been just right, you'll also hit some you shouldn't have hit had it patterned dead center. You don't have that same margin of error with a rifle, but you still check.

The only problem a double can have that a single barreled shotgun can't have is cross firing.