User blog comment:Xilinoc/Ch. 569 (You've been hit by / You've been struck by / Senbonzakura~)/@comment-7079377-20140221113541/@comment-7079377-20140221201640

If he did then why didn't he use it against Driscoll Berci? He would have had no reason to hold back. Plus Kensei said they needed more Shinigami with Bankai, therefore suggesting that Hisagi did not have it prior to the training.

Because of this I believe that Shūhei has learnt it inbetween the invasions.