As fuxia noted, winning percentages depend on how strong the players are, not just the opening.
Think about someone likely to play the four knights as White. Since the opening is rather unambitious and fairly easy to learn, there's a good chance this player isn't very strong. I'm not trying to generalize all players here, I'm just talking about averages. Meanwhile, Black is just following the main line moves for 1...e5. This gives no indication of Black being a weaker player.
As an aside though, the 365chess database isn't the most accurate. There are way more than 3723 games played in 4...Bc5. A look at the MEGA database or TWIC would give you more reasonable stats.