Yes it's to ventilate the back without telling away too much that it's a twin engine. There is a low pressure area right behind the wing which will help draw a lot of air out of the rear engine bay.
I really like how that looks (and I am sure performs). I have my entire trunk gutted and am tempted to do a similar mod now so I can get more pull through ventilation in the car when I have the windows down!
1998 GTP sedan: sold, 1999 GTP coupe #1: sold, 1999 GTP coupe #2 on E85: totalled
2002 GTP sedan: 3" downpipe|PLOG|poly mts|160 T*|60# Injectors|ZZP Intake|1.8 YT RRs|Ported Gen3|Ported ZZP S2 TB|E85|FP rewire|ZZP FSIC|WP UD Pulley|2.8 MPS|HP-Tuners