I'm going to go against common wisdom here and state that the shaved lead ring, not the lube over the ball that prevents chain fires
That's a safe bet, since the common wisdom really is that a proper fitting ball, not grease, is chain fire prevention. Most people with more than 30 minutes experience understand that the best insurance against a chain fire is the proper size ball (the lead ring is the evidence that the ball fits properly) AND proper fitting caps. Both are needed, as the chain fire can occur from a leak of plasma at either end.