Back knee is in a full vertical position at contact. If the torso pulls the knee along (regardless of hip openness) would you not then assume the knee would never make it to this point? How does the torso get that much movement below the hip if the hip doesn't open fully? Either the knee is moving forward and taking the hip from the bottom up in conjunction with the torso doing the same from the top down, or the knee starts the process and the top half is reacting to this movement.