Why is a straight shot assumed to be the perfect firing angle?

[fireship4]

Why is it that a straight shot is assumed to be the perfect firing angle?

I used to believe that this was because if a torpedo has to turn this will add an error but im not 100 percent sure now - isnt the "torpedo reach" or "torpedo advance" as it's called taken into account? I'm sure you can see it on the attack map.

Would it not be a better solution to have yourself on the target's course and fire when the range is smallest and the track is close to 90 degrees off his bow? This way you can use bow and stern tubes almost simultaneously - maybe bow shots wait a few more seconds until track reaches 90 degrees on the map, i don't know - better than turning around.

Maybe there is some mixup between AOB and gyroangle. I was about to call this thread "why is 90 degrees assumed to be the best shot" but i guess thats because the ship presents his full side to you and you have more chance of hitting. But this doesn't mean you have to shoot straight aswell...

Or maybe im wrong and having a gyroangle causes error.

UPDATE I tried it from 1000 yards at a stationary target with 8 tubes simultaneously. All hit. Text in below picture that is unclear says "20 deg off perfect angle".

Next I will try a moving target...