Why do explosive rockets claim to do less damage?

According to the in-game stats and all the wikis I've found, the two types of rockets are:

Rocket
Damage: 60 Explosion

Explosive rocket
Damage: 40 Explosion

Why would I want to research and craft explosive rockets, if they do less damage? It sounds like perhaps explosive rockets have a bigger blast radius, but nobody's actually said that.

Regular rockets do their 60 damage to a single target. Explosive rockets do 40 damage to everything in a circle centered on the target (there is no falloff). While this allows doing much more total damage, it can hit things you don't want to hit, and is not more effective against a single enemy.

The pictured test (current “stable” version, 0.10.12) shows that that the radius of the explosion is apparently 6 tiles. All of the pipe sections took exactly 40 damage.

(Note that unlike the shotgun, rockets cannot be fired in an arbitrary direction; you must target an object.)