A deflex riser bow is naturally a more stable shooting platform than a reflex riser. The grip pivot is in front of the limb pivots and cam. It holds steady because everything from the string to cams to limb pivots to the grip are all being pulled into alignment. The mechanical advantage is substantially reduced, which pretty much removes one pivot point from the equation.
I agree, that statement pretty much sums it up. Thanks Art.
Any imperfections in form will be magnified with a reflexed riser which puts the grip behind the limb pivots.