You used to hear this explanation for the commoness of left wing feathers a lot when I was youner. Most turkey feathers come from commercially raised birds. It is common to clip the wing feathers so that they can't fly. Since most people are right handed, the natural way to hold a turkey is so the worker can use his right hand to do the clipping, which just happens to make the right wing the obvious one to clip.This leaves only the left wing feathers for usage. I have no idea if this is valid, but at least it does sound reasonable. Any turkey farmers out there to comment on this possibility?
As for performance, I agree that either right or left wing feathers work just fine. I have never noticed any difference, nor have I had the issues that some of the guys have reported.