I don't buy it. We are all keen to see the "anti porpoising" magic bullet and speculation about anything odd in the floor will quickly associatie wit porpoising.
Joining the ranks of the "picture aerodynamicists", my guess would be that is is just a very clever device, repurposing the rule for the edge wing to make something to controll the airflow in that region. They managed to get a sort of strake in to really force some things. Shaping surfaces only gets you limited control.
It looks like the little kick on the end really powers up the diffuser bottom vortex, sealing it.
More speculative, it looks like it seperates the main tunnel from a mini tunnel to the outside of the device, including its own kickline (and thus different pressure) which the device neatly seperates.
If you have this device it needs to be metal, because it will touch the asphalt hitting kerbs. That does not mean it was intended to do so to prevent porpoising.