I think there is misunderstanding about the concept.
Insulating the compartment for hot weather usage prevents the cold from the camper to escape via compartment open to exterior air.
This way the compartment stays hot -eventually making fridge working harder and warmer.
My Fleetwood had Styrofoam insulation on those walls from the factory.
Couple years ago I did tests on my fridge and it was giving -6 in freezer and +1F refrigerator on 103F afternoon, when empty camper interior was at 99F and fridge wall was facing south.
Not bad for 18 yo fridge.
I simply keep the fins clean and check top vent screen.
