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If it's that, then imo Blackbeard is really the only one who is the exception to the statement, due to his growth over the timeskip, unless Oda pulls a "hasn't gone all out yet" card with Shanks or Big Mom, which I find unlikely.
I also saw the second half of your post before you removed it. You're right that other top tiers don't really seem to care about Kaido being the strongest and have no problems fighting with him. However the same could be said for Mihawk. While Mihawk is the world's strongest swordsman, Vista didn't hesiste to clash blades with him and Vista showed no fear towards him.
That being said, I would have preferred if Oda simply put Kaido being the strongest in an intro box so he could stop wasting everyone's time tbh. But alas.