Ser Rodrik isn't here to yell at Robb for going for the impressive, flashy move rather than the practical one, so that's what he does: he feints like he's about to strike from the right, then twists around to strike from the left. It's definitely flashy, and in a real fight against a real person instead of a dummy it would get him killed, but he already did die, so.

Then he hears someone else, and turns to nod to Kirk. "I was taught well," he says. "Were you waiting to use this?" And he jerks a thumb over to said dummy, which looks pretty banged up at this point.