The two ice chambers in the back have the center divider held off the bottom by a few inches. The fan pulls warm air off the top, down through the first chamber and the up through the next ice chamber and shoots cool air into the main chamber.
That is what I am saying does one need to be at top and the other at bottom
If you did this you could not control the temp. The cold air would always be entering the main fermentation chamber. With the openings both at the top, the only time cool air gets into the chamber is when the thermostat kicks in and the fan blows air into the main chamber. It is amazing how well you can control the temp of one of these.