[acme911]

Did a little more digging and found this site and after market product:
https://www.horsepowerfreaks.com/moshammer-rear-bumper-air-vent-porsche-991-turbo-%7C-turbo-s-14-16-p-151359562.html

Explanation:
"The Moshammer Porsche 991 Turbo rear vent is taken straight from the Porsche GT3 to vent hot engine air from the vehicle. Heat soak is an issue in any vehicle and Moshammer knows how to give your Porsche 991 Turbo the best in styling and functional components. With air flow coming in from the top of the decklid, this rear vent also helps pull away the hot air that can collect. "

Wonder if this is Marketing hype or mirrors the reason Porsche installed grill on original GT3?