It appears that whatever routine determines a ship’s speed for to-hit purposes doesn’t consider all situations where a ship might be traveling at less than its maximum possible speed.
I tried an anti-rush tactic where I had 1 line of ships ram the rushers and lock them in an immobile scrum. My idea was that by stopping the rushers in their tracks, they’d be much easier to hit than when they’re running around free. Well, I got the scrum I wanted but it made no difference at all in hitting the rushers. I was still missing them just as much as if they were on the loose. Methinks this is a bug.