So the secret to this conundrum can be found by examining the Goliath, and the Goliath merc.
The Goliath Merc uses ground while the Goliath uses Air.
So why doe the Thor use ground?
If we actually look at the Thor we see that the Thor actually acquires with its weapons based on angle.
On the Goliath and Goliath merc, these values are set to distance. Since the Thor can use angle to prioritize (Colossus and Goliath are both ground), it does. Since the Goliath can't (distance is identical), it defaults to the order its weapons occur.
Finally, this explains the Scout:
