Nope, you're all wrong - it's the coriolis effect. Try it in the the opposite hemisphere and you'll see...
This is really nice!!!
you increase the angle of attack of the downward moving blade, thereby increasing lift/thrust and producing a yawing moment" (p-factor, or asymmetric blade effect)
Here is the answer.
I've flown C152,C172,PA28,BA33,DV20,DA40, this effect is difficult to observe durring flare.
Then I've tried Tecnam P20002JF, an a/c with MTOW of 580Kg and 100hp. You really need to steep right rudder durring flare even in still air in order to mantain your nose inside the RWY.