In order to win a duel in the tournament, one must get knocked out or surrender—simple rules on the tongue, but complex to execute.
Submitting meant giving up the fight willingly, without getting defeated or fighting till the last stand—a choice few duelists would make willingly, especially with their pride on the line. No one would like to appear weak on the dueling ground, especially since there are lots of gangsters around—they can become an easy target for gangsters.
As for a knockout, it could be achieved in two ways: either by being rendered unconscious or by being forcibly thrown away from the platform.
Although Crusher's iron golem familiar had been knocked off the platform earlier, it wasn't counted as a loss because Crusher himself remained firmly standing on the platform. According to tournament rules, it would not be counted as a defeat as long as the combatant stays within the bounds of the platform, regardless of their familiar's position.
