It's an outlier. In the Pilaf arc, Roshi's Max KHH only destroyed a mountain. Going from mountain to moon tier would be an astronomical power increase which Roshi for sure didn't make.
If the KHH flew straight, and because Roshi is aiming slightly up at the mountain, then the KHH would pass over Earth as the curvature of the planet makes the ground drop below the range of the KHH. Same principle as Vegeta only hitting Cell with the Final Flash.
Keep in mind that, proportionally speaking, the Earth is smoother than a Cue ball. If you scaled the Earth down to the size of a Cue ball, it would be the smoothest Cue ball in existence. That means a projectile or path leaving the surface in a straight line would only hit the most nearest objects.
Aside from that, it is generally believed that DB characters can control the area of effect of their attacks. Even ignoring the moon feat, once they get to planet level, anytime they fire a blast that hits the planet that was meant to damage someone else that was planet level and up, and the planet is intact, the only logical conclusion is that the blast area was contained to prevent the damage from affecting the planet.
If they control the AOE for planet level blasts and up, they should be able to do it for blasts under planet level.