It’s all kind of ironic, actually, because in 2009 the regulations were changed to try and improve following and overtaking (sound familiar?). So, they change the rules so that the very middle section of front wing has to have a neutral shape. They do this because this area was bound to lose the most downforce when behind another car (since it’s more in the middle of the car), and by having it make little to no downforce, theoretically the perceived loss in downforce is very low when behind another car, so following should be improved. So, they made the first 250mm from the car centerline (Y, ergo Y-250) unable to have wing elements. You may know that where there’s a wing, there are wingtip vortices. Because the wings now “start” at the Y-250 vortex, we then had wingtip vortices, and thus, the famous Y-250 vortex, the cause of much dirty air, was born. This effect was very powerful, and made the bargeboards and under-nose cape work very efficiently, effectively sealing them away from the dirty tire wake. The same effect was used on the floor and the funky vortex generators that they used to have in front of the rear tires, and is still used in the rear brake ducts to seal the diffuser (these brake ducts were severely clipped in 2021, and were a huge reason why Mercedes were slower). A good visual representation of the Y-250: