The more I read the more I am convinced it has to do with managing what aerodynamicists call inner flow. It has to do with keeping the car more stable.
I believe in part thru pressurising the inside and cockpit and where they manage the exhaust of such inner air could also be used to feed that air where they want. Possibly to help manage that air/exhaust flow, towards the rear wing/diffuser, serving double duty. It's not a bullet so you must let some air through.
My opinion and worth everything you paid for it.