I think its clear to most people that Zoro and Sanji are clearly indicated to be Luffy’s number 2 and number 3.
Where it gets weird is when one is trying to powerscale through metaphorical titles, especially when I don’t think it even works that way. I am not a bird expert but I would think that saying a bird need equally strong wings to fly is the same as saying a human needs equally strong legs to walk and run.
it should be clear whose number 2 and number 3.