I think those small U shaped cutouts are to prevent that vibrations of the blade cause snapping of blade. We surely don't know what's exactly below the nose but I'm sure that blade certainly isn't touching the nose so there's probably some specific shaped cavity as you called it.
Something like SA06 or old Arrows but much less dramatic and exposed. Sort of front diffuser meant to enable good functioning of front wing despite extremely low nose.
Also, don't forget that this wasn't a test but just a show off for the press. Perhaps an hole will appear on nose used on real testing which would completely explain where the air from the center of the blade ends up.