I just had new weatherstripping installed. If your reffering to the header weatherstrip, then it does attach to the top itself, not to the windshield frame. Now 50resto does sell the thin weatherstripping that goes around the exterior of your windshield between the glass and frame.
The pictures on the 50 website can be really miss-leading when you start shopping for weather stripping.
The piece you are looking at must really be the header portion. Also, be aware that the 50resto stuff is slightly thiner than the OEM weatherstriping, so be prepared to adjust your J-hooks.