Backing with weight distribution hitch

I visited a airstream dealer last week to buy a reese weight distribution hitch. They told me, '' Its only a forward motion hitch and not to back up with it''. Is this true ? Does everyone disengage the trunnion bars before backing up? I don't remember reading this on the forum, but I also can't remember what I had for breakfast.;) Who can back up with their hitch without breaking something? This website is the reason I own a airstream. Thank you Gregg