The consult was in open warfare with the Kiniuri for 23 years before they summoned Mog. The North was then crushed over the next 12 years until they mankind was driven to the very edge of the inhabited continent. And remember, no children were born during the time the no-god was on the material plane. The sranc had no such problems, indeed they seem fecund and likely reproduced even faster when driven by Mog's will.
I think it not far-fetched to suppose that the majority of males remaining able to walk and hold a spear in Earwa were in Anaxophus V's army. There were no children below the age of 13 left at this point.
The glossary does state that attrition forced Mog to the field, but I think it was the attrition of men, not sranc, and that the transformation of the battleplain to a topos was the prelude to the culmination of the consult's final solution rather than the result of Mog's destruction.