A mass salvo could still be torpedo sniping

Why call a full Japanese torpedo broadside a snipe rather than simply a mass attack?

Because it was a long-range strike at a predicted target position; firing many torpedoes changed the volume, not the underlying method.

A viewer notes that Japanese destroyers fired full broadsides so that at least some torpedoes might hit. This was a mass volley, but it still counts as sniping because it was delivered at long range against a predicted target position. Volume increased the odds without changing the basic geometry of the attack. British methods tended to close the range and use gunfire or radar to fix the target before launching.