Well that's what theorizing based on visual evidence from the series does. You have to come to some sort of conclusion. What do you conclude when you have 2 wildly different results from photon torpedoes portrayed on screen. The original topic is what came to mind. The on screen results didn't make any sense.That doesn't seem to have stopped you from drawing a solid conclusion.
How can a torpedo exploded mid flight be able to take out two alien vessels from that alien species in "Work Force".
Also similar torpedo take out multiple Bio-ships.
Each Bio-Ship being vastly more powerful than a Borg Cube!
The only conclusion that I can draw is that they haven't been using the torpedo properly this whole time.