Garp was shown training his haki against mountains don't try to act like Garp's primary fighting method isn't his haki coated hands. Show me the panels of him fighting with his sword, as far as I can remember(which could be incomplete that's why I'm not stating these as fact) we've never seen Shanks fight so neither of us could produce panels of him fighting. I could produce panels of him(presumably) using haki back in chapter 1 rather than a weapon against the Sea King and on WB's ship he used his haki. There's far more panels out showing Shanks displaying haki then there are showing him sword fighting I'd bet. His sword is his primary weapon like WB's Bisento is his primary weapon but that doesn't make them their primary or even strongest method of fighting, WB's fruit is stronger than his weapon and he amplifies his weapon with his fruit.
Classified by who? Oda never classified his fighting styles. Haki man/master is a term created by fans to describe characters who use haki as a primary means of offense and defense. Being a haki man means exactly as it sounds, you rely on exceling in one form of haki to grant you an edge in battle. Enel's priests used CoO to help avoid damage, Vergo used CoA to boost his defense and damage. A haki man is someone who doesn't rely on their own tools for the majority of their fighting method. Zoro has haki but doesn't typically use it where as the other 2 I mentioned constantly used it in battle.
