How does the strategy of attacking a support unit in a skirmish work?

Question

I found strategy guide here that states:

Killing supporting unit Imagine you want to kill a special unit (say, a hero) but don’t have the force to kill all units in his area. Let’s imagine you want to kill the Gantrithor, supported by a Zealot. Now, your enemy will be confident since the Gantrithor can’t be splashed by simply killing off the Zealot, a tactic you would normally use. But there is another way: simply set a air-unit like the Valkyrie against the Zealot. It shouldn’t be hard to penetrate its health, and then the supporting unit will be destroyed. The only defense against such things except of course to avoid these pairings in your areas is to build the Defense Module.

I understand that the Gantrithor should be immune to ground splash damage since the Zealot is a ground unit.

However the Valkyrie can only target air so it can't target the Zealot, did I miss a rule somewhere? Can you attack a support like this? Or is it just an air splash damage that triggers? You normally need to kill the front line unit for a splash to happen, if this was a Wraith I could see this working, but can someone help?

Edit:(I did miss a rule) The strategy is done WITHOUT using splash damage at all, see bolded part in the answer.

Answer 1

I've had a response here From a user named: David F:

It's invoking this rule. Bolded the part that's relevant for this.

rulebookwrote: Front-Line Unit Combat Capability Effects When resolving a skirmish, if a player’s final attack strength equals or exceeds the final health value of the enemy, that player’s attack is said to have “sufficient strength,” meaning that he normally will destroy an enemy unit in the skirmish. However, the involved units’ types, combat capabilities, and arrangement in the skirmish will affect whether and which figures are actually destroyed. The following factors govern this determination, and are considered during the “Destroy Units and Discard Cards” step of skirmish resolution.

• If a player has sufficient strength, and his front-line unit’s combat capability allows it to target the opponent’s front-line unit, the opposing front-line unit is destroyed. (The combat rules and examples on pages 26–33 assume this.)

- If a player has sufficient strength, and his front-line unit’s combat capability is unable to target the opponent’s front-line unit, but is able to target one of the opposing supporting units in the same skirmish, such a supporting unit is destroyed instead. (If multiple opposing supporting units are possible targets, the player who controls those units selects which one is destroyed.)

• If a player has sufficient strength, and his front-line unit is unable to target any opposing unit in the skirmish, no opposing units are destroyed.

Deliberately put a Valkyrie in front, go "oh sorry I can't hit the Zealot. I guess I'll hit the air unit behind it then".

To counter this, use the Defensive Module from Brood War (ruled here that you can switch units within the same skirmish).