the databooks are made by the mangaka... he renders all the assumptions and "facts" anyone makes about Kenpachi's zanpakto not being released worthless. Even if it goes against everything he writes, if he states that his zanpakto is always in shikai.. it is always in shikai. In volume 14 Yoruichi asks Ichigo if he has notice his zanpakto is always released and he says "really?, so is like Kenpachi's zanpakto?" and yoruichi didnt say no or correct him... the one that STATED his zanpakto is always released is kenpachi, the conversation Ichigo and Yuroichi have just confirms that Kenpachi zanpakto is always released. Because he doesnt know its name, kenpachis riatsu and the swords power are "in conflict" if u may causing Kenpachi's power to be unbalanced but my guess is that he finally was able to talk to his sword and know its name.