Oddly enough, I write left handed, use a spoon left handed, fork in left hand knife in right, yet I am utterly right handed when it comes to using a computer mouse (doing complicated and intricate graphics work) or on the odd occasion I've played cricket or golf.
It's not that odd, I'm the same (though for different tasks). I think it has something to do with my previous point about lefties having to adopt some rightie tendencies out of necessity (ever tried using 'normal' scissors left handed?).
It is curious, but as others have attested to in this thread it seems easier to use a yolk ambidextrously than it does a stick. I wonder if that is the primary reason that most side-by-side flightdecks use this system, which again makes me wonder about the C-17 and Airbus.