Rebuild license plate holder on Switzerland?

Hello people, the front plate holder is known to be bigger in the EU than in Switzerland. I see it more often in Switzerland that the small plate holder is simply mounted on the big one. Is this for convenience of the owner or is it not better? What hides behind the black holder? Is the part fixed with 4 screws (see picture) to the bumper (then it won’t work)? mfg grani