first i dun believe everything i see on the internet
second it look silly to do that in real life
thirdly, the hot air is coming towards the person who is opening and closing the door, which mean he will feel hotter.
When the interior of car heated by the sun, not just the air is hot, everything inside get hot, removing hot air alone is possible will not solved the problem. The solution is to remotely activated air con before you get into the car.