I have a Asus U33JC (i5) laptop and I just added the same card to it (replacing an Intel Wireless-N 1000) and I am seeing the same thing. I am getting decent speeds (780Mbit/sec a few meters from the router) but Windows still doesn't know about "11ac".
I'm not unhappy, I just find it strange that Windows 7 doesn't recognise 11ac.