Well that Garp should be a good example for you to know that Oda values his statements more than ever changing portrayal.
When he constantly tells you Mihawk shakes the grand line, calls Mihawk one armed has been, strongest swordsman ever, Black Blade, 3.6 Billion Bounty, More Sword Skills, Legend Among Men, Waiting for Swordsman stronger than Shanks.
When Oda stops being lazy, he will give Mihawk that one portrayal that will make everything Shanks has done, look like a joke in comparison.