There's conflicting logic here. On the one hand, Devin would appreciate being left to himself and appearing uninteresting might be enough to shake his hanger-on. On the other, lying could land him in a situation he liked even less than this and the other man appears to be persistent enough to push through a lie for the sake of entertainment.

"I'm capable of it, in the right circumstances," he allows after a moment, giving Melek a narrow look. "At most, I would have broken a few bones; thievery doesn't earn the kind of punishments I typically mete out."

So technically the answer was both; he was bluffing, after a fashion, but Devin would and could do it if he chose to.