Leonard's goals and assists ratio is fairly balanced, and not similar to Caufield for example which is highly biased towards goals. Smith and Perreault run the PP for the US program, meaning they are fed the puck and they distribute it. As a consequence, they will always get more points, as they get more touches. Leonard plays a different role on the PP, and even at 5vs5 to some extent.
One interesting statistic about Leonard is that he has the highest +/- ratio per game among the three players. So, although they are getting significantly more points, the other two players are on the ice for much more goals against than Leonard. I think this is an important stat, especially in the context where these three guys are oftentimes on the ice together.