It’s the rising pulley that halves the applied braking effort. A force of say 40 pounds pulling the pulley up in its slot applies 20 pounds to each brake. But the same force applied to the ‘wiffle tree’ type twin-pull lever goes to both brakes. If you look at a Vincent scissor action front brake mechanism you will see that it is a much better idea than the late-Shipley Scott thing, where the movement of the cable is halved by the pulley. The Brum Scott/Royal Enfield handlebar lever doesn’t halve the linear movement of the cable, and neither does the Vincent version.