I have raced on treated and untreated rings and the efficiency and reliability is actually slightly better with untreated rings. The reason for pins and gates is to allow the chain to fall off the rings at given aligned points, making it a reliable and predictable process. In adverse conditions, such as rock gardens or slalom or the like, a treated ring can be a liability since it will shift easier. Intentional or not.
For normal conditions, there are few reasons to go with untreated rings. Untreated can be a hassle to shift with, particularly on uphill shifts(which are hard anyway).