User blog comment:Xilinoc/Ch. 554 - Desperate Lights/@comment-1248963-20131024011641/@comment-5657895-20131025231427

Shinji telling people what his sword does is not awesome stuff. That what got him cut when he faced Aizen.

But Yhwach is also cooler than Aizen. Much more ruthless, brutal, dangerous, actually accomplishes things, isn't completely heartless, so I can forgive him the all knowing nonsense.

As for stealing the Bankai I think it was a measure to take the Shinigami off guard during the first battle and claim victory without revealing too much about their real strength. Think about it, in that battle they killed the most powerful Shinigami in existence and had the Shinigami focus on all the wrong things, like fighting without a bankai, only to have their hard work prove to be nothing and get their asses handed to them a second time.