OK, all I know is that my grill was an unmolested standard (non-RT) grill. The rivets were aluminum and hollow and black. I still have some of them, maybe I'll pic-n-post. As for the paint after assembly theory, that was just that.. a theory, based on the missing silver paint on the underside of the insert on both sides where there is step in the plastic. Incidentally, there is a black stripe that goes on the inside of the inserts, but only half way around. Again I'm basing all of this on a NON-RT grill that had never been touched. Maybe the paint scheme was different for an RT grill.
I see two things in the purple RT above that are different from my orginal grill. The black stripe on the inside of the insert is not there. (If this grill had been painted then I would understand because this stripe will be difficult to duplicate), and second, the tips of the rivet tabs on my inserts were painted black.