F1technical.net

What's wrong with the geometry of those VGs? And how can you tell they're wrong from a photo when the teams have spent hours in CFD / wind tunnel playing with them before mounting them on the car?

They're intended to interact with the rear tire, the fact they don't race them means they're not having the intended results, and this serves as more or less a correlation study for further development.

Your limited CFD and windtunnel time is better off going into more important/long lead time parts than it is something you can just roughly guess what you want it to do, 3D print some in a day and just stick 'em on the car to see what it does in practice.