It is in spec, but it wouldn't hurt to push the tops out a little bit. You could have them tell their alignment machine it is a regular F-150 instead of a Lightning, but that might even be in spec for an F-150. Do you have a printout of your readings you could post? There's a pretty good chance that they just don't want to mess with it since it's in spec.
FWIW, camber doesn't wear tires, it just determines where they wear. If they are wearing too fast you either have a toe problem somewhere or you are working the front of the truck really hard.