I have a signature pre prod model and it has a metal bar at the bottom but no able catcher. At least for my case I can use the original 2 piece aeroshield just need to tuck in the lip under the bumper at the bottom front. I don't know how this will work with ankle catcher but I'm guessing similar thing (do the original splash shield wrap around the ankle catcher in those cars? ).
The 1 piece costs around $280 at tesla and to me it's not justified.