I didn't look into it, but I'm pretty certain that's just bare steel at the end. I don't know what kind of coating could be formed by a laser other than "black rust" which is nigh-on impossible to remove compared to the normal red or brown rust. However, one of the conditions for black rust to form is limited oxygen in the affected area (look under your vinyl top or between pinchwelds). There's plenty of oxygen available to the part in the video, and it does not appear to be blackening either.