Still not sure I understand the advice you were given about rotating your shoulders as you lift your leg. I believe you were advised to counter rotate your shoulders which I believe will also result in counter rotation of the hips. I would proceed with caution. Rather than giving my own opinion I’ve lifted a portion of a Steven Ellis piece titled “23 pitching mistakes (you’re probably making)”. Excerpt as follows.
"8. Turning your back to the target.
Sorry, not everyone can be like Hideo Nomo. While he was pretty successful with this technique, it is not a recommended method for most pitchers.
Turning your back and shoulder at the peak your leg lift causes several issues. First, turning your shoulders obviously moves them away from the target. While it’s important to have your lead hip closed at the peak of your leg lift, it’s still important to have your shoulders aimed at the target.
Rotating will cause accuracy problem because it may actually force a pitcher to pull too far to the glove side. You will notice pitchers who rotate the shoulders too far will often miss to the outside portion of the strikezone. It can also make it very difficult for the throwing arm to catch up with the rest of the body."
JMO, any movement away from the target is wasted movement.