Is there ever condensation within a roof vent cavity? – GreenBuildingAdvisor

Based on Martin’s answer here: https://www.greenbuildingadvisor.com/question/vented-attic-vapor-retarder US building codes do not require vented cathedral ceilings in zones 1-5 to have a vapor retarder (just need an air barrier). I also understand that the majority of roof moisture problems come from air leakage, not vapor diffusion. 

Assuming the ceiling is air tight, any incidental moisture from diffusion should be whisked outside via the vent cavity. Is there any mild condensation that may develop on the underside of the roof decking from that vapor as it passes through the vent cavity? Or are we really talking about almost unmeasurable amounts when in zones 1-5, assuming at least a 1.5” vent cavity and a 6/12 roof pitch?