Strongest Pirate and Strongest man are 2 completely different things lol.
Pirate could mean in terms of territory and influence.
this doesnt prove anything except that Whitebeard was better at being a pirate
edit : Which btw makes sense since Kaido has been in Wano and isnt actively claiming territory and stuff like that
Strongest Pirate... as in out of all the pirates, this one is the strongest. "Better as a pirate" that is so disingenuous and contrary to Whitebeard's portrayal. Please stop.
Also just because Kaido has been in Wano, doesn't mean he hasnt had his crew been claiming territory elsewhere. It's completely assumptive to say that.
Strongest means STRONGEST for a reason. They don't say "Best, or better"
If thats what they meant, that's what they'd say.