The fundamentals is that they;
try to keep the barrel UP (not pull it rearward),
they try to keep the hands and barrel back until their shoulders start to turn, and then they snap/throw the barrel at the ball.
They shift their weight by pushing off of the back foot, and turn the hips before they throw the barrel.
Not a complete list, but the basics.
Bold above, do you really think shoulder turning launches the hands? Or are you relaying what a MLB thinks when swinging?