If the is no vacuum due to a leak, the flow director defaults to defrost and all the A/C or heat comes out there. If you have partial flow, I would suspect a small vacuum leak.
Too much coffee today ? Yes, there are two holes in the defrost door, the one closer to outer edge is about 1/2 inch, and the other one is about 3/4 inch.
It is a little more important in Tucson than Colorado but if that is factory as everything appears it is, I can consider other ways to block the defroster outlet. We don't use defroster much here.