I'm saying when Zoro cleaved Monet in 2, there was no Haki involved there..
Actually CoA Barrier is not needed for a Swordsman to cut everything and nothing as shown in Alabasta.. Plus CoA Barrier with a Sword would '' not cut '' no touch, not, '' not cut '' touching which is not Swordsmanship..
I don't know about the Rokushiki.. Zoro was not using ryou(haki) to produce air slashes.. I can see Kamie being CoO, Tekkai was shown to be CoA, Rokuogan could be Internal Destruction.. Those are reasonable, but Shigan, Rankyaku and Geppou seems to be only strenght related..
It's not as strong as a theory, it's an hypothesis that makes sense.. Can Ashura come from Sandai Kitetsu?.. Yes it can..
There's no conclusive evidence that Ashura is from Zoro and not from Sandai, so i don't have to provide evidence on something that can't be verified, as long as my hypothesis is logical it's fine..
Anime is filler, so it's irrelevant.. If Zoro had those Haki, he would say oh so Luffy can use that too or something like that..