Even before 'captains only' we have had wide discretion in how we want to manage players. We could (should) give dissent cautions for being surrounded or for players refusing instructions to go away if we want to speak with the captain alone, regardless of a specific rule. Competitions have to stick to their own rulebooks so may not be in a position to take their own enforcement action this season, but encouragement and monitoring can help to achieve good compliance levels even without enforcement.
