if you go back into the archives you will see this question. I asked this same question when I did the BH Cleanse. Since I fasted with this, there was no question it was MP. The benenite clay absorbes the toxins away from the intestinal wall. The fiber scrapes and scrubs cleansing the wall. A lot of MP also has mucous. That is a result of the diet you have.
When explaining this process to a family member who was totally repulsed by the fact I would show her my MP was this.. if you have ever looked down your bathroom sink drain.. often you can see this nasty black build up. Sometimes your sink will even plug off because of the sludge. Well our intestinal walls are no different. If we don't take active steps to clean the walls, then MP starts to build up.
If you start eating again while doing PB shakes you will see how your bm will take the shape of your intestines but will be regular bm brown color. There is no mistake in MP and just regular BM's. Hope that helps.