Board Thread:General Discussion/@comment-4957813-20131130185522/@comment-24974663-20140807003145

The argument is Dual Zanpakutō. That refers to TWO SPIRITUAL manifestations, not how many physical components are involved in the PHYSICAL appearance of the weapon.

Katen Kyōkotsu, Sōgyo no Kotowari & Zangetsu are the only Zanpakutō to have two distinct spiritual beings that manifest as the wielders Zanpakutō. Zabimaru and Kazeshini only manifest as single entities, despite having multiple components in the physical weapon. The former only being confusing because it has two voices, despite being one body & one weapon.

The argument has nothing to do with "dual swords." The Katana shape just happens to be the 'typical' sealed state of Zanpakutō. That is the end of the argument. No other swords meet that criteria.