Board Thread:Questions and Answers/@comment-27392440-20160221191403/@comment-26091912-20160307075837

Yes it is.

It's not that Nanao didn't need an Asauchi, it's more that an Asauchi is needed to forge a Zanpakuto, regardless of who wields it. But in this case, hers is the only Zanpakuto that is handed down generation to generation.