Katakuri fought against people strong enough to give him Future Sight, which not even Kaido and Big Mom have.
Those words imply training for many many years instead of haki blooming in an extreme battle condition.
Also if Katakuri had fought guys on the top tier level,why would he be undefeated?
Kaido doesn't have Fs as you said but was shown to be able to deal with it on the rooftop.
Mihawk too,the strongest warlord isn't implied nor portrayed to have it yet,do you think he will be stalemated by Katakuri because of that?