I think the resting period also helps the smoke particles on the surface move into the meat, evening out the flavors and mellowing it slightly.
Will, even I let ribs rest for about 15 minutes, covered in foil. Just like a steak on the grill, a brief period to let the meat relax, and reverse the outward flow of juices (even though ribs aren't typically "dripping"), seems to help the texture and tenderness....or, at least, it seems to in my mind. Kind of "optional," for ribs, but I think it helps a bit.
Rest ribs??? ha! they are lucky to get from the smoker to the counter in my house! haha