That may depend on how you measure bouncy. I don't think there's enough energy lost in the compression and rebound of billiard balls that you would ever notice. I suppose it is possible that the balls could be harder and the time of contact between the balls would be reduced, but I also doubt there is enough squish in any decent set of balls that anyone could notice. Assuming there is a noticeable difference between these and other balls, it is probably that the surface finish is more durable, or the anti-static properties reduce chalk sticking to the ball, perhaps eliminating some wear and scuffing, and reducing skids.