You can check it out easily, just attack an Ogre or a Bone Ogre, put your tank next to them, and have at least one other squishy target. They will target the squishy target, even if they are far away. It happens every time, it only requires one of your own units to be next to the Ogre or Bone Ogre that it DOESN'T want to attack, and a preferred target further away. It will act like Crushing Blow is a ranged attack and can attack any of your units.