Not a truck on the place, nor any I have ever owned, have had that black plastic thingie that is on the one pictured.
What purpose does it serve ??
RATTLE RATTLE RATTLE RATTLE RATTLE
WOOSH WOOSH WOOSH WOOSH
Eliminates one of the above or both. WOOSH is wind noise.
Just in case you don't know, the tailgate has the same thing on the latches. It don't go WOOSH only RATTLE.