Board Thread:Questions and Answers/@comment-32617252-20180806022624/@comment-36486151-20180806145649

Aizen didn't lie. This was what he himself believed.

The Visoreds suffered from Soul Suicide. Urahara simply cured them of it. It was never confirmed if Tosen suffered from Soul Suicide.

Soul Suicide wasn't a criteria either for being a perfect Arrancar either. The Vizards were inferior to Tosen. Unlike Tosen, they can't use Arrancar abilities like Descorrer, Resurreccion and High-Speed Regeneration. Aizen reffered the Visored as failed mock Arrancar, logically Tosen would be successful mock-Arrancar then.