Many people put the band just around the right leg and there is still the left cuff. Myself I cover the drivetrain in one way or another on every bike, so I neither need to bother with stained pants nor bands. In any case, it would be interesting to know whether the Arundel knob creates a problem for the cuffs. Overall this cage makes sense.
I could leave the left leg off and try it. From a safety standpoint, it makes sense to have a reflective band on the left leg since that is the side facing traffic (in the US). The cage works for me because my coffee cup won't fit in a regular cage. For weekend rides with a regular water bottle, a standard cage is more convenient. But I can make the Arundel work. I have been working about 500 miles from home this year and I only have my commuter (Surly LHT) and my Brompton with me.