[UKönig]

I think those pictures clearly illustrate the effectiveness of the hedgehog launcher.
In a type VII or IX, at creep speed, like 1-3 knots, you aren't going to be fast enough to get out of the way. No dashing to the left or right, or staying straight ahead. If you are moving at flank speed, like 7 knots, then you are making enough racket that they can use their regular 500lbs bombs without relying on the hedgehog system. Really, only the type XXI had the dash ability to get out of the way in time, and they were never used in battle.