It is specific. For example it lists the Vindicator Tank, whose datasheet is found in the SM Codex. It doesn't say Vindicator Tank Destroyers, who have a different datasheet found in a totally different publication. It is exactly what it says it is. To take another example from the Angel's Blade Formations, the Lucifer Armoured Task Force lists a requirement as 3-5 squadrons of Baal Predators or Predators in any combination; not just Predator tanks.
That being said there's nothing at all stopping you from playing the game however you want with your friends or discussing FW options with TOs at tournaments.
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