Hi gap,
I was also hoping that there is only a single firing 'animation'
IIRC, the K-gun was always fired at the same moment as the other K-guns on the escort; no matter where it was positioned.
When testing the hedgehog parameters for the squid I also found out that the position of the launcher mattered: Depending on the distance of the launcher from the ship's center the projectiles were ahead or behind the target. My guess is that the game only takes the ship's position into account when firing/dropping DCs (and the u-boat's speed, but not the hedgehog firing range and the sinking speed).
Best, LGN1