and you are correct, what i essentially meant to say though is that casualties increase in a disproportionate manner, for example let's say a heavy armored spearman would take 20% more casualties after a mass increase, a militia unit would take 80% more not 20%
you could say that mass increase causes cavalry to always attempt to kill more, when a knight charges a footman if the footman doesnt die the knight keeps going forward and pushes aside the soldier he cant kill and then hits another footman thus attempting to kill again, high mass causes the knight's charge to keep going for longer and trying to kill again and again instead of stopping after hiting the first unit he cant kill