Some say what you are saying TBC. But others say, and I am am with this crowd, that the art of decoying is attracting and the funnelling of birds to within good close shooting distances. As for the "J" it works plain and simple from my experience. They were talking J Hooks over 30 years ago and still are. And puddlers like to land in "holes" of the decoy spread. Thus the U works as does "pods" or family groups of ducks with space between them.
Very similar is duck calling---how often have you heard a Mallard give a high ball call? It is not natural, but it works to get their attention. How often have you seen a duck just hovering with its wings spinning? But it works when using a spinner. Decoying, calling, etc are attention getters to lure birds in-simple as that.