Your quote: Wrong!! Since we're talking about a 10" barrel in a pistol with a much slower fps than the 35" barrel with a faster fps. They both turn the ball 1/2 turn in the barrel. At 100yds which one do you think will turn the ball more times? How about 25yds?
Answer: Velocity has nothing to do with the number of turns. The rate of twist determines that. Velocity only determines how long it will take for the projectile to get there.
25 yards (900") 100 yards (3600")
1:20 45 rotations 180 rotations
1:70 12.86 rotations 51.43 rotations

Pete there is no insulting by me only by you. - Please look at what both you and I are saying. We are both correct. You are saying that in a 35" barrel with a 1:70 twist the projectile will make 1/2 turn and in a 10" barrel with a 1:20 twist the projectile will also make 1/2 turn. You are correct. However they are not turning at the same rate.
Out of a 35" barrel that ball from the 1:20 twist will have made almost 2 full turns whereas if the ball was shot out of a 10" barrel with a 1:70 twist the ball will only rotate less than 1/4 turn.
And if you read my post and comprehend what I am saying my thoughts are that the faster twist is required due to the lesser velocity from the lighter charge.
As for the effects of twist rate in a barrel I don't think I can explain it any simpler. Barrel length has absolutely nothing to do with twist rate. The twist rate of the rifling in the barrel, whether the barrel is short or long, determines how fast the projectile will rotate. Maybe someone else can try to explain it better.