Far from a retrograde step in the design, it is an improvement. Instead of an exposed and separate screw on the adjustment knob on an AXMC, that required more parts and assembly, it is now a one piece machined part. As you can see from the photos below, the first one shows the original adjustment knob and the other two show the new style - you can still use the hex wrench to put torque on it to tighten it, if necessary.