Quote Originally Posted by Drolyt View Post
Presumably either Isshin's bankai is different, or else most people didn't know about it. I'm fuzzy on the time scales, Isshin had to have become captain after Turn Back the Pendulum since it was there stated that the 10th division captain had died while in the current flashback those events have already occurred. Since it isn't clear when Byakuya became captain, if Isshin became captain first then Byakuya may never have seen Isshin's bankai.
not to mention "energy blast" isnt a terribly unique ability.