You do have a point. For all we know the wind tunnel tests could all be a simulation for marketing; however, there are members who say that it helps so I guess there's some substance to the claims..
As for Tesla, they can't even add in a simple blind spot indicator, so it'd be hard to give them the benefit of the doubt to do anything beyond bare minimum. As we know for them it's all about cost cutting. Perhaps the current spec of the spoilers on the Performance models are the bare minimum length, before crossing over into the no gain territory?
I would like to see a test of someone 3D printing a spoiler to extend further out from the UP one and to see how much that helps. In theory, the more tear drop shape the car is, the better the drag co-efficiency should be.
This is why the IONIQ 6 is designed the way that it is with the aggressive rear slope and duck bill spoilers making it one of the lowest drag co-efficiency EVs. 0.20 iirc.
Very curious now. Anyone have a 3D printer? I'll bring the drinks.