That's certainly possible as well. The only thing militating against it, IMO, is that her summoners sacrificed themselves to bring her about, at least on the NA version of the dialogue with Hythlodaeus, and would be sundered along with everyone else in any case even if they were not. But who knows, maybe she identified and revived them.
The reason I thought the description is consistent with the Convocation is to do with how the First Umbral Calamity and the First Umbral era are described here, with the "gods" basically vanishing at this point. Especially since they were initially reduced to 13 due to the departure of the 14th (at least until they filled the office), and then again to 12 with Elidibus forming Zodiark's "heart", and possibly going on a recruiting scheme to gradually fill their ranks (in line with the gods gradually emerging), thus being absent on the Source. There is also some overlap between Emet-Selch's traits and those of Nald'thal. Much of what we now know of the Twelve seems to be the product of myths which arose over time, and of course this faith also enabled Louisoix to almost draw on their power through a near summoning of them as Primals.