Just for the sake of a clearer understanding and being that CBMP is more important than CBM. Obviously the person asking does not know. It would have been far better to have put your last sentence first and that is CBMP is associated with stepping outside partner sometimes written as O/S Partner. Being that it is most important and used all the time. It should then be pointed out that stepping outside the partner with no CBMP. there will be too much of the hips of both exposed. Then it should be explaned that CBMP A term used when the body is not turned, but the leg is is placed across the body. Which to me is the shoulder is in place and the foot is placed across the front or behind. The third step of a Feather is a classic example where the step is placed across the body on the toe.
The cold facts are. You can dance to a fair standard without worrying about CBM. But without CBMP it becomes quite ugly.