Hi, the idea of the void was to enable the ease of a lot of cables to be run without damaging the sip or any other boards & making life easer to install the many miles of cables that will be fitted. There will be nearly 3.5 miles of cat5 cabling alone going into this one.

Convective loops form when warmer air rises within a enclosed space (over 3/4"), cools and descends, where it is warmed again creating a complete circuit.  The loop does not rely on infiltration to form.  Running the furring strips horizontal would prevent convective loops.