Pull out front license plugs?

[hinten]

What I don't understand is: If these pieces are designed for the front hitch why don't they all have the vertical pin holes? Did Hummer go a different direction with their front hitch design? I assumed that all trailer hitches have the horizontal pin and all front hitches have the vertical pin.

Also, I have a hitch attachment for bikes and such. I though I could use it on the front hitch but I guess I can't because of the pin placement.