if you think to bump your hips forward then you run the risk of swaying and messing up the approach to the ball. when your front hip gets outside of your left foot most all people get in trouble because the hips will not turn properly when the weight gets onto the the outside of the front foot so by bumping them 30 you may take care of some of that issue. Now if you go to the top of the backswing and you shift your weight DOWN onto your front foot then that will "bump" the hips and you wont have to worry as much as getting outside of the front foot, which is a swing killer. when the left foot gets the weight the energy now moves up from the foot and this is how you post the left leg. If you just move your hips you may end up not posting your left leg.

that being said, if you do that right, and have a fairly on plane backswing, focus on coming into the ball from 1-2 dimples inside of the center of the back of the ball, you wont need to ask about the secondary axis tilt coming into the ball.

try posting the left leg from the thigh down and then try it from the ground up. tell me what you find

what did nicklaus say,
he said ar first he did not understand why his instrucror made him do boringng footwork drills but later realized why it was so important.

hope I helped