User blog comment:Xilinoc/Ch. 565 (Mangapanda is run by lazy barnacles)/@comment-1268838-20140122195654/@comment-5693502-20140123075734

KawaTsuyo I see what you're saying. But I think that Yhwach is a higher entity and the Quincy are just what resulted when he shared a deeper part of his soul with certain humans. In essence they are a sub-set or sub-species (at best) to whatever species Yhwach is. Because of that Yhwach can't be a Quincy, in a similar way to Lucifer and demons (if you watch Supernatural you'll understand my connection).

I've said it before, but I think Yhwach's core power is more Fullbring-like than anything else. The 'Quincy' power he displays was probably not his to begin with but was instead stolen as a result of using Auswählen multiple times.