You're just being argumentative...
And only speaking half truths.
Isn't enough room for the air to move around?
We are trying to prevent air from going under the car by lowering!
Squishing the air? Really?
We are lowering the car, not just lowering the rear and creating a wedge shape under the car...
A smooth underside that raises towards the rear causes low pressure, pulling the car down, and of course, increasing drag...
I'm sure each car is going to be different in the results, but generally, lowering helps.
Check this out...apparently it's been posted a few times! Lol....
Car Aerodynamics - Hot Rod Magazine