The fight was short but Jan was mapping Corey´s movements, and he noted the awkward way Corey positions his body to give more power to his kicks. So he left the left leg as a bait and waited for Corey to come for it. In one of the gifs you can see that when Corey kicks with the right leg, his head is AHEAD of his left knee. As if he was asking to be KOed. And Jan complied. This, in my view, is the beauty of training, and a fighter´s ability to read his opponent.