There is a precendent in the T'au Codex FAQ where an item that was once wargear and is now a Stratagem isn't allowed to be used through the Index legacy route.
So need to stick with the Stratagem version only for this one.
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From a midnight sky, there is a searing flash, a boom, a brief moment of destruction, and then it is gone.
Kabal of Lightning Strikes - Project Log
Drukhari damage output analysis