Board Thread:General Discussion/@comment-24815992-20140414144050/@comment-11051098-20140414154058

If I remember correctly, Shinigami who has achieved Bankai does not need to say the name of the Zanpakutô to release its Shikai.

Regarding your last question, I don't know. It's a filler arc, so I guess they thought that since he played mute due to his light voice, he could get away with releasing his Shikai without saying the name.