Thanks I get you. This is a close up image outside, underneath frame where it meets sill. So even a thin line of silicone (mimicking the blue line) to stop rain driving in between frame and sill would cause issues with the concealed drainage holes? I wasn't planning to put silicone blocking the whole of the bottom of the frame.Your window frames are hollow. There will be holes where screws have gone through the frame, if the runner seals arent perfect, etc.
If any water gets into the frame there are holes in the bottom of the frame (not visible once installed), to allow the water to exit the frame and run out onto the window sill to the outside and then away.
Fortytwo is correct, if you silicone the outside that water can’t escape and you’ll cause more problems.
Hope that makes sense