The way I understand them they force the shank down. They wrap around the top of the shank, then put pressure upward from the underside of the receiver, sucking the shank down, the way you would want it.
When it comes to my WD hitch, that thing creeps and moans enough that rattle is not an issue. And it applies pressure itself with the arm bars directly to the receiver through the hitch shank. (I believe this is upward pressure on the WD shank). Either way, I never get annoying rattle with my WD hitch, at least nothing that I notice. Although I have been known to shove a wood shim into the gap between the shank and the receiver, or wrap some flex seal tape around the solid shank if there was a big gap. The rubber or wood dampen the metal to metal banging noise.
When it come to hollow shanks, especially for cargo carriers that rattle around like bb's in a tin can, I'll cast another vote for the Let's Go Aero. Those are awesome!
ETA: A final option would be to use the 2.5”-2” reducer sleeve and use a 2” WD shank. Then use a 2” hitch clamp. The reducer and smaller shank might put the clamp far enough down from the bumper not that you wouldn’t get any scratches on the bumper. As far as I know, 2” shanks are just about as strong as 2.5” shanks. Especially when it comes to solid shanks. Just a thought.