The boundary layer of air that builds up on the underside of the nose isn’t moving, so it isn’t adding to the downforce, only preventing air from following the contours of the underside of the nose. The slot allows the skimming of this boundary layer, which allows the moving air to attach and follow the body is intended, which of course increases downforce. Its a good idea and one that works well, red bull have a slot in the same place, for the same reason, but their has a complex ‘s duct’ that ducts the air to the slot on the top of the chassis, which helps the air coming off the step in the nose to re attach to the chassis. Red bull have run their solution in both rounds so far, its anyone’s guess why ferrari haven’t run theirs. I’m more interested in the different exhaust outlet designs. I like the red bull ‘ramp’ design, but I see the benefits of using the ferrari/mclaren design, as far as getting air under it goes, I would love to know for sure which is better, they both have upsides and downsides. The nose slots on the other hand are pretty basic, teams have used similar solutions for years now.