I know it's probably headcannon, but the strenght behind that desert espada at 6:37 makes me think it was empowered by haki. And it wouldn't make sense for a warlord to not even know how to use it (Even if that concept probably didn't exist back at that point of the story)
Why would it have to be powered by haki? It was just sand shaped into a blade. If anything, luffy used Haki to prevent his fist from getting cut up. Although of course he didn't learn it yet. Perhaps he used it subconsciously.
I'm not sure about this attack but yeah the lightnings do look like the visuals for armament haki we have now. But even if it may not have been as fleshed out as a concept as it is now I'm sure Oda had the baseline ideas for haki in mind by that point. Or else Logia users would have just been invincible barring the silly "i can throw water at them" thing. Heck the whole Zoro vs Mr 1 fight was all about the early concept of haki imo, with what Zoro says about feeling things, cutting what he wants & being able to dodge falling debris without looking. And then we had Mantra at Skypiea 1 arc later !
