Keith from KNC says:
There has been a slight revision in our casing that we had neglected to previously explain.
The case has had an airflow improvement to ensure increased thermal efficiency.
We have ensured the hot air from the front two heatsinks is redirected, avoiding the rear chips, and is expelled from the casing by installing fins affixed to the upper casing section (despite appearing in the CAD as part of the lower section of casing). In turn this allows a sufficient amount of cool air exits to ensure a cooler operating environment for the rear heatsinks to operate comfortably.
What I don't understand is why they didn't make a wider case with all four modules side by side instead of trying to direct the air with baffles.