This is nothing more than an observation, so I have no explanation in terms of physics or physiology.
I've noticed that, in great shooters and in myself, it helps to have a more NARROW base (or to bring the feet closer together in the air/upon landing). I've tested this out myself and with clients, and always get great results. Shots seem to go straight more consistently with narrow feet than with a wide base.
There are reasons why it helps to START with a wide base, but I always seem to shoot far better when I start narrow (like Steph), so I adopted a consistently narrow stance. I've found that's it's easier and faster to get shots up without having to worry about getting a wide stance and getting low. I also don't believe in deep knee bends, so these things pair well. Perhaps narrow feet allow you to extend more or have better balance in the air.
Anybody think they have a good explanation for why this may be?