Just because the DOT inspection passed doesn't mean it's the safest place to clip it.
It's purpose is to activate the electric brakes if the trailer separates. I sure can't predict how the trailer will separate, so it seem sensible to me to make it as independent from the hitch as possible. On my cars, the box receiver is bolted to the frame separate from the bumper - so I attach the cable to the bumper mounts. That way about the only way for the trailer to separate and not trigger the brakes would be for the frame to break. That's a risk I have to live with. :)