If the shaft really bent that way, wouldn't it produce other effects that we could see? I'd think that the shaft would eventually snap back (or snap, period!) and start oscillating. There's also the question, which I'm sure mandrin could answer, of how much force such a bend would represent and whether there's enough muscle mass in the fingers to retain it.
I think the illusion hypothesis is the simplest explanation, but it's always possible (from watching old Tom Mix movies) that wagons can go forward while their wheels are turning backwards.
