User blog comment:Xilinoc/Ch. 618 - The Dark Arm/@comment-2211792-20150309051438

Someone pointed out that since Aizen still has his disintegrating reiatsu, the Hogyoku didn't really make him a normal Shinigami as he supposedly wished. Ichigo was wrong.

Also, when Kyoraku earlier complained that Aizen wouldn't talk to him using reiatsu, could it be that he just couldn't sense it? Aizen being transcendent and all.