What, in that case, prevents us from changing the wording so that red-rush is only forbidden when attacking an opponent's town/garrison/hero containing more than 30% of their forces, for example? This way, you could hit scout heroes and towns with trash, but not the main forces. After all, you can even see by eye who you are hitting — a scout hero, a reinforcement caravan, or the main force.
The 30% option doesn't work because you don't know the total power to calculate 30% from it. And asking your opponent while the timer is ticking is not very convenient.
