And how exactly is he supposed to hold onto that title if he isn't the strongest in the verse? If you're dubbed the "King of the Pirates" and someone comes to challenge your right to be called that, and they beat you in a fight, then who is going to acknowledge you as such after you've lost? To be King of the Pirates means you stand at the pinnacle of the Pirate World. I don't know where people get the impression that you can be anything less than the Strongest and still be Pirate King.