User blog comment:Xilinoc/Everything but the Rain op. 10 - "Prinz von Licht"/@comment-1387259-20130515140418

I'm going to come out and say I highly doubt Uryū is actually allying himself with the Vandenreich. Over the course of the last 9 chapters, Ryūken probably told him all the same stuff that Isshin told Ichigo. Unlike Ichigo, Uryū probably wanted more answers, and thinks he can feign allegiance with Yhwach in order to beat answers out of him.

This, however, is all just a guess.