It already happened...
WB in MF
WB was definitely the strongest man in the world at that time, he got the gura who allows him to destroy the world, top 1 strength and every form of haki, not as much as he might have before for sure but it doesn't mean he lost his spot. He got shot, stabbed took canon balls, got half his face deleted and a hole in the chest but still stood 10 toes deep into the ground, not even bowing down to death itself. In my opinion that sounds more like a you problem. Funnily enough, Bb the character who actually discuss the reality of his title get immediately shat on.
You have to also consider if these titles were for sales in the first place, no one took on the mantle of wsm after wb's death for example. On the contrary, being the wss is canonically a competition in the manga with zoro and shanks serving as contenders for the title. But ultimately the peak of swordsmanship is a black blade something only mihawk achieved, this is a concrete evidence of his undeniable legitimacy.