The "cooldown" in the 3oC is for rapidly killing Ultras. More than likely, just a nerf to 3oC when killing the SAME Ultra over and over (Draksis, I'm looking at you). So by killing a loop of different Ultras, and even going as far as doing it on different planets, he is keeping the "cooldown" from initiating. I've been holding on to many of the Ultra checkpoints from the story missions since 3oC came about and when it's been a while since I've killed an Ultra, I usually load up one of them, pop a 3oC, kill the Ultra, and then leave. It seems I've gotten exotic drops fairly consistently doing this, so I can see his farming method being legit.