I’ve only ever seen that on cars with a CD changer and doesn’t exist on those without. CD changers at the time would get warm and if they didn’t have a vent then they’d be a fire hazard. The material around the changer functions as trim/noise reduction so needed an actual vent.
Personally I didn’t like the installation location which is why I never specced it on my first A2, I just settled for changing more frequently from the head unit.