The article basically states that you should train specifically for the demands of your sport. MMA is performed at a very high intensity and therefore, training should mimic that. Why do you think Franklin, Wanderlei, Lesnar, Sherk etc. are all doing 5 minute, high intensity circuits on those spike all access training specials. I have yet to see an all access where they just showed the fighter casually jogging at a light pace on the treadmill.
Also, we have different types of muscles fibers (fast twitch, slow twitch and fibers that can be altered to take characteristics of either one depending on what sort of activity we do.)
If you're always doing low intensity cardio then your distribution of slow twitch (endurance fibers) will increase. This is actually quite undesirable for a professional fighter that relies on power and explosiveness to knock people out and win fights.
Anyway, if you're fighting 3 five minute rounds with a 1 minute rest inverval, then it only makes sense that your training mimic that as closely as possible.