Kaido and Yamato do have a very eastern aesthetic, unlike most of his crew who look like barbarians. Plus Kaido himself refers to haki as “ryou.” I know he’s been on Wano for two decades plus, but he was already a pirate for years outside of that, and was surrounded by senior peers who’ve used the term haki.
There’s definitely more to Kaido’s background which relates to Wano. And his respect for Samurai must run deeper than simply meeting Oden.