Board Thread:General Discussion/@comment-9732657-20130519011726/@comment-8986886-20130619184217

Omniguy183 wrote: ^He even called White a hollow based off of a shinigami's soul. Which means he's a hollow.

I believe Aizen waited until he had the finished 'product' before naming it Arrancar; so all experimental samples preceding it were simply referred to as Hollows.

Kaname said that White was completely different from all the types of Hollows they had created so far; being the first one created based on the soul of a Shinigami.

Kaname also said that White didn't just undergo Hollowfication, but it actually managed to achieve its final form; which indicates that White was something 'more' than just a Hollow.