I am not an aero expert, but this is just what I feel. It appears as if there is too much of unmanaged airflow at the rear that is creating, more than necessary drag while exiting the car. So, it seems like a desperate attempt to break the pressure and reduce the drag at the rear. It is quite possible that, they are simply unable to send as much pressured air to rear as they want and efficiently handle what they are sending.
Reading this sentence aloud will probably create more worrisome drag than anything affixed to that diffuser.
The element highlighted in yellow is likely intended to divert air flow that might otherwise pass over the diffuser to instead be fed to the force-enhancing edge vortex. The flaps that extend across the width of the diffuser help to "drive" it in much the same way beam wings were formerly used to "drive" diffusers.
There's nothing untoward going on here.
The difference between the Ferrari diffuser and those seen on the McLaren and Red Bull is a difference in philosophy. McBull appears to seek peak downforce; Ferrari appears to seek consistent downforce.
giantfan10 wrote:Running more wing than other cars on average shoots the assumption that they have great aero right in the foot
No. Just no.