i can tell you they have gotten better at making the enclosure air tight!
i had one heck of a time getting my fridge out for repair, all of the cabinet seams from the factory were sealed with lots of silicone. the face of the fridge was/is sealed with weather stripping and the bottom gap is filled with silicone to boot!
reasonably air tight is the answer to your question.
here is a thread on my fridge with some photos that may help.