User blog comment:Xilinoc/Ch. 586 - The Headless Star 5/@comment-11506376-20140625171259/@comment-24306779-20140626122858

I wouldn't be so sure about all of the Sternritter being Echt Quincy. As Nodt is seen in a hospital bed in a critical condition before Ywach shows himself, saying "It seems you're one of the survivors" and recruiting him. Considering that Uryu's Mother, a Gemischt Quincy, was in a similar state after Auswählen, it's possible to theorize he was also a survivor of Ywach's purge and, deemed strong enough to follow him, was allowed to join their ranks.