Yes, that is correct and the T&Cs confirm as much: "Benefits of membership will only be awarded on Qualifying Stays. Qualifying means that your reservation is made directly with us (via web or phone) and not through sites such as Hotwire.com, Priceline.com, Expedia.com, Hotels.com, Travelocity.com, Orbitz.com, etc."

What with lowest price guarantees, most if not all hotel chains are no longer crediting bookings through third parties.