The last chapter ended with Rocks, Kaido, and Whitebeard confronting Imu. We know that Rocks will die, and Kaido and Whitebeard will receive the World's Strongest titles. I believe the World(MU) itself grants the World's Strongest Titles. However, this is the main catch: receiving the World's Strongest title means acknowledging the World's authority. Rocks refused to acknowledge the World's authority, for which he was executed by Imu. Roger and Garp received the glory of having killed Rocks as a reward for their strength being recognized by the World itself. However, unlike Whitebeard and Kaido, the World did not grant them the World's Strongest titles, as both Garp and Roger are descendants of the D-Clan.
Mihawk also holds the World's Strongest Swordsman title, meaning he once met the World in this world and was defeated by him, revealing his power, but losing the battle.
Thus, being the Strongest in the World doesn't mean that one is the strongest, but rather that the WORLD has recognized one's strength, and the bearer of the Title recognizes the WORLD above them.
Mihawk also holds the World's Strongest Swordsman title, meaning he once met the World in this world and was defeated by him, revealing his power, but losing the battle.
Thus, being the Strongest in the World doesn't mean that one is the strongest, but rather that the WORLD has recognized one's strength, and the bearer of the Title recognizes the WORLD above them.
