User blog comment:StonerCatJay/Rereading the series- theories and speculation/@comment-4207271-20140522011541/@comment-24963493-20140522013804

I hadn't thought of the cons you mentioned, though I think they can both be explained with the fact that his powers were so intertwined, they even shared the same spiritual body. It could just be that there was enough of Zangetsu within his bankai to affect his shinigami powers, but that it wasn't truly a bankai.

I could also just be grasping at straws at this point, but I still think it's possible.