Here it is. Mihawk is not a swordsman. He used a pocket knife against a swordsman who challenged him for the WSS title .
The fact he keeps the knife around his neck means he is prepared to use it against challengers.
Seriously. King words were true even early in the manga so nothing has changed.
King: Is there a need for stuff like styles & forms in battle?
He simply saying a swordsman is free to use whatever style they wishes to use in battle. Oda let everyone know anybody who claimed a fighter can't be a swordsman because they have and use another power like a DF power is wrong. If the pure swordsmanship claim was true Oda would have had King said he's not a swordsman.
This chapter elevates Mihawk's title so everybody who's claimed Mihawk isn't really strong because he can't beat characters that use a swordsmanship plus other powers or wrong. Oda just them to shut up and sit their ass down.