5" wide plan view side skirts?

Latest FasTrack has proposal that side skirts could be 5" wide when viewed from above.

Trying to figure out why any car needs that. Shouldn't they be limited to not exceed the outer edge of the tire?

At least that is how I would interpret a plan view....

Or are we folding it back under the car that far?

My take was to keep someone from creating a flat bottom across the car.