User blog comment:Xilinoc/Ch. 642 - BABY, HOLD YOUR HAND 5 (EYES ARE OPEN)/@comment-6657474-20150911134944/@comment-24531362-20150912060603

The way I understand the statement, Mayuri's Bankai is somehow artificial or augmented. Ichigo and Urahara achieved Bankai, but Mayuri probably made his.