He's right. Corsair does recommend this as one of the possible fan configurations because you do get better CPU temps. The problem is that everything else will be hot inside the case, so it all depends on your cases airflow and what you care about. If your graphics cards can handle the extra temp and you want the most out of your CPU, you can do it the way he does it.
But this is a so-called "gaming build"; therefore, his graphics card is more than likely taking more of the brunt than his CPU... consequently requiring the graphics card to stay cooler.