Thats odd. Im pretty sure they have to cover it if you have comp unless there's some obscure line in your policy stating otherwise. Usually the worst news you'll get is that your policy doesn't mandate oem glass or your deductible is higher than the replacement cost.
if I could remember correctly, the very first time I called to have my windshield replaced, they told me that because Colorado has a lot of glass claims, that the only thing they do cover is the rock chip repair...I may have to call them back and find out again to re-verify