User blog comment:Xilinoc/Ch. 680 - THE END 2/@comment-25192437-20160701070423/@comment-24531362-20160701215050

Yhwach stole all of Ichigo's native powers, the ones he was born with. He was born with his Quincy and Hollow facets, so those got stolen. His Shinigami powers were learned, and thus cannot technically be stolen.

As for the second bit, I've personally been of the opinion all along that Yhwach is not actually a Quincy himself, but is just the progenitor of the Quincy race; this would explain why he's called 'Father of the Quincy' and not 'The First Quincy'. Also, dude has straight up eaten god, thrice, at this point. Even if he was a Quincy before, I don't think those rules apply to him anymore.