Seems my dealership is trying to exclude cladding from warranty work also.
I recently lost both 'diamond' plates on the rear bumpers where the steps are (the small ones). Not sure when I lost them, but when I brought it into the dealer, they said that it couldn't be a warranty issue becuase I lost both of them, and besides, there was snow in the trailer hitch, indicating I must have backed up into a snow bank.
Now, there's no damage to the rest of the bumper, and if pushing a little bit of snow causes the plastic to come apart, that is a concern to me. It's very possible this happened on one of the days it was 30 below.
I'm a little anoyed at the dealer and will probably fix my bumper with carriage bolts for now. I'll let him deal with the two $60 covers (their quote), after checking gmpartsdirect I think they ordered the wrong ones.
I think that even if they took the time to order the correct parts, I would still be annoyed at them.