I've just realised something while reading through the Kaido Vivre card thread.
When Mihawk was introduced into the story, he was referred to as the world's strongest 3 times in the span of 2 chapters; his intro box officially called him the WSS, and later Sanji and Zeff both referred to him as the world's strongest.
In comparison, since Kaido's introduction, the only time Kaido was referred to as the strongest without his title being treated like a rumor, was when Killer recently called him the strongest pirate.
What reason does Oda have to disrespect Kaido like that?