Yep, I did some testing before and absolutely noticed this also across other compounds. I had a speculation it was due to the rigidity of the wheel mesh and the more rigid it is, the worse the contact patch. When I used 15+ in particularly high powered cars it was like driving on glass.
That’s why the techpool on the wheel tab is strictly set to 0.
I suppose so, but I wanted to allow people to select the variation themselves instead of cheesing the downforce. With a limited number of fixtures that simulates the limited aero efficiency available as one then has to choose the balance between drag and reducing lift.