Drip cap is used whenever water running down a wallcan get behind a horizontal surface. Such as behind a door or window, or when the door or window has a non-integral flange at front or back or both.
This article says that even windows with an integral plastic nailing fin benefit from a drip cap.
This seems to be folklore, not correct. How does a drip cap benefit if it sends water away from fully water-proof plastic?
This is prior to sealing nailing fin with butyl tape.
Can you tell me what the drip cap is doing in this case? My conclusion is - nothing.
Window Water Instrusion
Properly designed windows let in water around the gaskets (but not likely at the panes themselves). Windows are designed to let this water back to the outside from the frame area: