CO is applying some algorithm based on your individual performance and torque metrics.
CO’s history is Bioshift: Xert and Bioshift – A History – Xert
I think fast twitch/slow twitch composition and your physical build are contributing factors.
Some cyclists are natural spinners. Others are not.
IME CO has lowered my inclination to spin fast for no good reason. 
From what I can tell this corresponds to a lower HR for a sustained power output. More efficient?
On the other hand there is no way I can sit in on an A/B group ride for long without high rpm.