User blog comment:Xilinoc/Ch. 540 - The Sword Five/@comment-3246134-20130606184056/@comment-1043846-20130608044840

Yes, he's far from perfect, but hey, Yoruichi has seen Zangetsu. I know, she is young, but surely she's heard of Yhwach and knows his appearance. And she could relay to Urahara. I just think he discarded it as a nonsense, since Yhwach was still sealed at the time.