To me this is to provide support to items stored in the refrigerator. We always placed some sort of device over wire shelves regardless if it is in the trailer or in a storage closest. Small items tend to tip over and to me the coverings support better than just wire shelves.
We have placed 1/8 LUNA board over all of the wire shelves in our home pantry to keep items from tipping over or falling thru the wire spacing.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, TDR 135K+miles