Kon walked up and barely hesitated as he "cut" his hand (ie dug into it with his fingertip until it bled and made it look like the knife had done it rather than blunting the damn thing). He dripped it onto the coals.

Unlike Cassie, in response to the hoots and hollers of Dauntless, Kon turned around and did thump his fists on his chest, letting out a loud whoop that could have come from Peter Pan himself, louder than any whoops or hollers they could have made. Then he trotted over to them and was met by a sea of high fives. (And one instance of Cassie slapping his ass).

Dauntless was supposed to be brave. It was supposed to be free. While the books had made it clear that the idea of it had gotten twisted away from the way it should've been, Kon was brave and free and he wanted to establish his dominance in that area from the start.

So they weren't surprised when he trounced them in Dauntless itself.

That was how it had always been. He could fly. He could fight. He could crow.