According to the author one should only use rudder when rolling in or out of a turn - while banked the aircraft does not need rudder and in fact use of the rudder causes it to descend and has to be compensated by excessive back pressure.
Langewiesche has a habit of oversimplifying and then asserting the oversimplification as truth. Some regard this as evidence of his didactic brilliance, others as unhelpful dogma. You might notice the following footnote: "Important fine points regarding the handling of stick and rudder in a turn are disregarded here, in order to let the main idea appear more clearly."
The aeroplane will generally slip if held at a constant angle of bank in a turn with rudder central. It's the yawing effect of that slip through directional stability that causes the nose to yaw around the turn as the direction of motion over the ground changes. It's perfectly possible to operate an aeroplane in that way. If you want to fly the aircraft in balance, you need to apply some rudder to provide an alternative source of yawing moment.