People read properly.
He said "tougher" not "stronger".
Like king was better in terms of speed and Defense. But kaidou was ofc objectively stronger.
Similarly
Shiryu would be far Superior than Blackbeard in some field that BB won't be touching. My guess is Haki and Hax (Clear Clear fruit).
With awakening , he becomes nothing , literally nothing and no amount of FS is gonna be helpful here.
And no way to attack them either , while he constantly attacks you with his barrage of Strong Haki attacks.
Zoro will be the only one to get the ability to cut everything and nothing at the same time.