Esme Nielsen. CBMP. If you can find an example of a Foxtrot on youtube by a top professional. You will see that on a Reverse Turn on step five the lady should be backing the wall and not backing diagnal to the wall. The man is the natural opposite
You can then see how step 6 with CBMP is performed. If the man turns too soon anti- clock you are not in CBMP. In fact there was no CBMP at all.
The person who wrote Keep your body facing your partner. would have been better if the had written . Keep your partner in front of you. Those are the words most used by professionals.
A much simpler way of showing CBMP to a beginner is to stand with the left hand ( right hand for the lady ) out to the side at arms length, palm facing the front which will be the wall in this case. Without moving the left side. Step across the body towards the palm of the left hand
CBMP is a foot position only because the side is already in position from the preceeding step. I hope this helps