Does concussion get a +4 to hit the ground?

[Kristoffer]

Explosive Fireball and Explosive Lightning specifically mentions that someone may choose to hit the ground instead of their foe for a +4. Concussion does not.

However concussion is stated to explode and does direct to the rules under explosions. In Exploits, Attacking an Area p. 45, it states explosions can deliberately target the area for +4. So since concussion is an explosion, it should also get the bonus.

So does concussion get +4 to hit the ground or not? Is it intentional that the spell doesn't state the bonus or is it just an oversight? I am in doubt, since concussion also grants a rather hefty stun, so it might be a balance thing.