Based on the corrected translation, the barrier haki skill Hyo taught Luffy is based on the 'Mighty blade' technique which is as Hyo says is what master swordsman use. The implication being people like Zoro would know the skill also. The original translation could have been interpreted as Hyo was considered 'The Mighty Blade' and he can teach Luffy a technique such as the barrier haki thingy, so the implication would be that Zoro didn't need to know it.