User blog comment:Xilinoc/Ch. 633 - FRIEND 3/@comment-8669536-20150702091412/@comment-2211792-20150702125700

There's a possibility that Auswahlen doesn't work like "absorb powers from everyone in this area" and that Yhwach actually chooses every victim himself. So Ichigo and his sisters weren't targeted on purpose.

It makes sense for Yhwach not to target Ichigo because he foresaw him killing the Soul King. As for his sisters... what if they don't have Quincy powers to begin with?