There is a gap in mine but only because I had to have my RT Mines-alike splitter trimmed back because I have a Zun-sport grille fitted. I took it all apart, painted my lower bumper bar black and then re-assembled as the GM bumper bar was, as you say, very obvious.
As far as I recall the splitter should actually cover the entire top side of the lower bumper bar - but RT Perf will give you a better answer than me!
David