The most important reason to do twist and turn in Kung Fu to'a is to challenge the gravity. That's why we must twist and turn with any technique. For example when we try to to do "Mato", in the beginning the back of the active hand is faced down, when it moves at the end the hand faces up. So it has to twist and turn 180 degrees.
Keep in mind that if you do any technique, even a small move without a twist and turn with your active arm and reactive one, it would be a wrong move or technique.