Rockets don't necessarily have more range but they travel in straight lines rather than in an arc so they can be used to hit higher targets more easily. They also don't travel as fast has normal munitions.
I tested each rocket type myself and can only see 2 damage for every heart. I shot myself and creatures multiple times to see if there was any damage variation; there is not. I believe that article is based on self damage from using rockets with the elytra.
Yeah, rockets definitely won't be replacing arrows, but they're good for hitting a group of targets and flying targets. Also loading a star with different effects can disorient players, perhaps even cause them to lag due to particle rendering.