I agree there is no meaningful thrust coming from the exhaust but disagree regarding the airflow. Yes, the air travelling past the exhaust will be faster than that coming out, but that there is air coming from the exhaust means it will collide with the laminar flow and it will create drag. Interestingly on the 1299 Ducati have angled the exhausts further aft.
I certainly agree with the weight saving/ less restriction aspect and imagine it could well produce more power. I imagine power/weight are more important to Termignoni than aerodynamics. I don't expect it will bother many, unless like me you enjoy the autobahn