While our system aims to get you into the game as fast as possible by only downloading what you need to get started, we also don't want to compromise your gaming experience to do so. Therefore, there is a larger than usual initial download for some games to ensure that you don't run into any issues.
While the start-up size may be larger than for other games, you will still get into the game faster than downloading everything first! The second time you start the game, it will already be ready to go due to the game being downloaded rather than streamed.
You can recognize which titles have larger starting downloads by the 'hourglass' icon seen in the client.