The r/d bows are glued up with such a profile and are tillered from the beginning with the starting profile in mind, so that stress is evenly distributed in the limbs. If a bow were tillered with stiff outer limbs to purposely create or allow set right after the fades, the wood would be overstrained there. The uneven distribution of stress would then be made worse by reflexing the outer limbs. Frets or a blown bow would likely be the result. Also, trying to induce reflex into limbs that have already taken set (collapsed belly wood cells) doesn't work too well. Off the caul, the reflex looks great, but it's quickly lost with a few tugs on the bowstring. Reflex is most effectively added during the pre-tiller stages.