When you're shooting at extremely close ranges like that, it's entirely possible for a torpedo to be very close to a valid target but not see it because the angle gets too extreme, or it turns the wrong way first when it begins its search pattern and by the time it takes its next turn the weapon has already passed the target. You definitely want to stay in fire control during a knife fight like that both to make sure your weapon is enabled at the right time, that the acquisition cone is facing in the right direction, and that one of them doesn't come back at you.
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