It was a tactical foul as he'd been absolutely roasted by Nisbet and the boy was clean through. He knew exactly where he was and what he was doing however a more street smart striker would've waited until he was in the box before going down.
A fine line between giving away a penalty (and subsequently being at fault for 3 goals in 3 matches) and giving away a free kick.
Strange decision giving him 2 years right now tbh. Cannot fault the boys effort & commitment along with his influence in and around the dressing room but I'd have waited to see how he gets on between now and Christmas before dishing out extensions.