So, the early Espada don't have to be "naturally" occurring arrancar just because they didn't use the Hougyoku, they could've been created by Aizen long ago.
Did Dordonii say "naturally" born arrancar?
I think he means Espada members, not the actually Espada group itself. I think the Espada grouping is purely Aizen himself and anything before Aizen were just adjucca's who became arancar by ripping their own masks off or by having someone interfere like Aizen or something.
A pie in the sky?
Ok.. so the question stands regarding the existence of the Old/'Natural' and New/Hougyoku Espada due to Neriel's appearance.
(P.S; similar to Yoruichi, Kisuke and Isshin's case no?... If so, I doubt Kubo will clear it out though)
KINGS-Of-A-Kind; The Baboon & The Panther