Great question! In the scenario you described with 3 players running an easy game it would be 6 rounds where everyone can act (in each round).
6-Minutes would actually be a hilarious way to play, and would be a great way to ensure that a game was within a certain time-limit the group has to play. The only concern there would that players would be talking over each other in an attempt to get the most out of whatever their character was doing and, although chaos is the name of the game here, that seems a bit overwhelming for the GM. If the players were all working together to enact a singular plan, I think it could work, though.