Melee and missile might be two separate systems. Melee might play animations based on combat results, as this makes more sense. Projectiles, on the other hand, might use a realistic physics engine to determine hits. If this is not the case, then why were there so many friendly fire issues in RTW? Archers could shoot their own front rankers in the back if the angle was too low. Onagers could demolish their own siege towers if they got in the way.