European vs. other P10 grilles

Hi, evryone.
I was wondering if your P10 grilles let the air through to the radiator. Mine does not (they are covered with plastic from the inside), so all cooling goes through the hole in the bumper. But I belive the Infiniti grilles let the air through. Why is that?

CU

The grill on my P10 Primera lets air through.

http://www.angelfire.com/sk/fordfalcon/Nissan.html