That 180 degree turn in the form....

In Cheng Man Ching's form, there is move where you turn 180 degrees, then raise both of your arms and do a push kick, striking with the heel. A little googling pinpoints it as Movement 40 or 42 in the the 108 Yang posture form.



My question is this: what is the point of the 180 degree turn??



I've read some people turn on the heel (which is what I do), and some say turn on the ball. I have an answer to this question, and why it is described when discussing applications to the form's movements. But I am wondering what are other people's take on this particular move.



Thank you all for your wisdom once again. I truly appreciate everyone's response on this forum.