Why would that be Chuck? Partly because of all the increased surface area in front of the CG, becoming affected by the slipstream, and your poor little rudder not being powerful enough to fight in a slip situation...
I thought it was because there is not enough side fuselage area and vertical fin area to counteract the added side area of the floats ahead of the vertical axis.
Thus the primary or most effective control surface to control adverse yaw would be?
When I first received my instructors rating over fifty years ago we were taught that attitudes and movements and effect of controls was the most important lesson in flight training and unless the student fully understood the subject and could demonstrate same we were not to move on to the next lesson.
Judging by what I observe flying with pilots now this seems to be ignored by far to many instructors.