Not just looking cool on TV, looking cool to the jury. I don't think it was dumb at all. It destroyed the morale of the other side and got in their heads, it was a psychological move. He would never have gotten the other half from her. If he didn't throw out the shell, there would have been a big drama back at camp when he refused to give it back which would have created a narrative that made him look bad and made him a target. Yeah, don't get that challenge. Might as well have done "I'm thinking of a number from 1 to 10".