It isn't for balance...but for the rpm at which resonance occurs. Everything resonates at a certain frequency. The more an engine sees this frequency the less time it will live....whether it be crank, piston, bearings etc...
The ring gear was added to avoid this at commonly seen rpm...what rpm that is I have no idea. And what lightening the clutch does to what rpm this occurs I have no idea, but any change in mass will undoubtably change this.
Some Polaris guys will add mass to the P-85 to increase the life of the clutch and crank. I ran the much lighter P-85 on a Doo 800R for a short time and lost a crank. It may have been a coincidence..?? I did notice much more vibration in the bars with the lighter clutch....and yes, it was balanced.
Many guys remove this ring and have no problems, I have heard from many others that have seen what they consider short crank life running lighter clutches. For myself, its not worth the gamble. I do vibration/resonance testing for a living so Im probably overly paranoid about these sorts of things, but having seen where small changes can make a huge difference in the life of a part I will not mess with something that works. JMO