Isn't the new thornmail sort of contradictory to it's purpose now?

UNIQUE PASSIVE - Thorns Upon being hit by a basic attack, reflects magic damage equal to 25 + 10% of your bonus Armor, inflicting Grievous Wounds on the attacker for 1 second. UNIQUE PASSIVE - Cold Steel When hit by basic attacks, cripples source’s attack speed by 15% for 1 second.

So...you're buying an item to counter sustain/auto attackers...but then you stop them from hitting you as much... so unless the GW applies on the actually attack that hits you (I don't think it does, pretty sure GW only applies on attacks after it's applied) that means that the GW will only matter on people with at least an attack speed of like 1.16 and that's if they're hitting you as soon as possible. Yeah I know lifesteal and AS usually go together, but that makes this item and it's component pointless for a tank to rush against a sustain opponent since it relies on the enemy getting items first.

Idk, I feel like this just doesn't really make sense together. There's already two armor items that slow AA, why does this need that when you actually WANT them to hit you more.