They're a pure rice mod and there's nothing wrong with that. It's not like any of lips, splitters, side steps, spoliers, cannards, snorkels, ducts, vents, diffusers, dildos or any other external mods are wind tunnel/CFD proven.
The only way these louvres, not some different ones on a different car, can be fitted to a car that is driven in the wet on the road, is on top of the glass. You could easily fit them instead of the glass if you drive your zed exclusively in the dry and don't mind creatures clambering in whilst it's in the garage or if you've got a track weapon with no interior to get soaked.