As the title suggests:
The Pahvan Torpedo does not display the Resonance Shock line when in Torpedo Spread Firing Mode:
This is a bug because it actually grant Resonance Shock to the enemy. But this is also bugged. Because High Yield will normally procs the Resonance Shock stack.
Torpedo Spread:
https://drive.google.com/file/d/1CwJo1wfRC07E-1Wi_RPQtC1JFzxs4rnp/view?usp=sharing
High Yield:
https://drive.google.com/file/d/1kFB6VddJp3HtoJi0fFvxsuzHs7OgwnFl/view?usp=sharing
Based on this information, I'm assuming the torpedo is bugged.
It is supposed to behave as the description says: