As JD pointed out natural convection will be low to high. Adding the fan above to move that hot air out is from an engineering perspective logical. Doing so puts the refer cabinet into a slight negative pressure condition.
On the flip side, for those of us with the three-way there is another more important reason that I feel needs to be considered.
The three-way units may be used on gas. Burning gas can, and does, omit some by-products that can harm. Like CO for example. If you set your fans up as a pusher (Moving air into the refer cabinet, and your seals on the cabin side are not perfect (And NONE of them are), you would be in effect giving the bad stuff a direct powered path into the cabin. You and your traveling partners may not wake up as a result........
This is why mechancal rooms are properly designed to be negative air pressure to occupied spaces.
If yours is pushing air into the refer cabinet, I emplore you to change it.
GJ