Loras didn't buy it, just like he hadn't bought that this had been Obi-Wan's first time. He half believed Obi, but he'd seen him do this before, during their first session. The grin told him that he was right, and he moved quickly out of the way, then brought his own bo to the backs of Obi-Wan's knees.
It was a kick boxing move, to duck and strike, and he may not even connect, but he still called, "Dirty tricks, old man!" Did a warrior use dirty tricks that often? Loras found it a warrior with respect for his opponent would, but they'd had trouble with that from the very beginning.