The difference with the Apple knob is that you would be given a strong cue for what to do after you tap on the knob. The current knob design has no cue until yo

The difference with the Apple knob is that you would be given a strong cue for what to do after you tap on the knob. The current knob design has no cue until you press and slide, when you see a value change. But you have to do it right before you get any cue. Real knobs are turned; not tapped, pressed or slid. The slider shows you an affordance that works. The knob shows you an affordance that does not.