User blog comment:Xilinoc/Ch. 592 - Marching Out the ZOMBIES 3/@comment-25252005-20140806101724/@comment-6657474-20140806104248

Probably more a case of the desperation of the situation they found themselves in. I seem to recall that just before Charlotte died from having his rietsu drained, that Yumickika stated he didn't even want Ikkaku to know the true form of his Zanpakto because of the 11th Division's unwritten rule about only allowing strictly melee type Zanpakto.