That, and most people do not really need a lock ring with a standard cog on the track, especially if you are as strong as Carleton. A couple of good accelerations and the cog will be on there tight (assuming you are not doing too many skid stops on the track!). I know people who race without a lock ring, thinking that in a crash – it might save their knees having a potential breakaway of the cog (allowing it to spin backwards under extreme load).
That is their excuse for not using a lock ring, at least…