The formation is not the only thing to affect your losses tho. The test proves that using the shieldwall against melee enemy infantry can help you by what - 25% losses saved? But with your ugprades, experience, general and more units in the battle, you will more likely save more men. Of course if enemy will push on one side with lots of heavy troops, you will suffer greatly, but still better to lose half of a single unit then half of an army