In a round about way, you are claiming that lefties playing right should be better players...
@BklynKen agree?
My own experience trying lefty, it was much more challenging than I expected. In part because I assumed that everything I learned right would transfer easily. It didn't. I think if I had the patience to stick with it longer, I would have made progress, but it would be like learning to play from square one all over again. The only advantage would be already knowing some songs.
I have thought that for a teacher, there would be an advantage to playing lefty. In demonstrating to a student, it would be like looking in a mirror, which is a view we are accustomed to. My teacher opined that the advantage to learning to play lefty would be empathy - having a recent memory of how difficult playing can be when it is new.