I changed weapon sway to 0 awhile ago. The only thing it did for me was make my gun sway back and forth very quickly. It gave the illusion that I was running. It didn't stop the gun from swaying at all, which was what I wanted to do at the time.
Interesting find though, myabe if I felt like it I could play around with it again. I just don't see how no weapon sway when your running can affect aim, since you cannot fire and run at the same time. And when you walk, stand still, I never really noticed a sway that affected my aim, or shooting.