I think Oda is never going to portray Luffy in the same manner as Kaido, Shanks, Whitebeard etc until it's time to fight the big bad, he still wants Luffy to be a goofy guy for the most part (which is fine, just won't suit people depending on their expectations)
Now that title merely means that they’re in contention to be the PK and Luffy is still the underdog cause Shanks and BB are still stronger and Buggy’s power to fall upwards just will get him to the top regardless of what happens.