he is not talking about quality/level just quantity.
My guess he is rushing the units, with lots of cash, he might got from other players for declaring war on you or trading some resources for cash.
Either way he pumps gildars into rushed units, with 5 cities, he can pump 5 units a turn, which if combined with the armies he got earlier, should be what you're seeing. I don't myself rush a lot, and if you're a player like me you spend your cash on buying leather for your heroes, which is something AI do not. (just look at his equipment, he probably have only starting sets on heroes plus one or two items gathered in quests, and possibly a couple of lether bracers)