The point about steering angles was, if I recall correctly, McLaren's 2018 car's steering disrupting the airflow to the sidepod and bargeboard i.e. they got the placement slightly wrong so when the car was cornering the airflow would inst
One thing that's kind of amusing, is that if you ask older members of FSAE (student racing car competition) teams, nearly everyone has a story about either themselves or a competing team designing an aero part only to discover that the part was basically just for the designer's curiosity/ego than any real aerodynamic performance on the car.
Airplanes do not fly at all unless designed holistically, which is why the Wright Flyer flew and the other attempts did not.