Sorry, I haven't heard of it myself.

I know when M was very bad with her food allergies and intolerances, she would poo 6-8 times a day and most vegetables came right back out the way they went in. It has more to do with her absorption than anything else, she also lost weight. I would suggest she find a gastrointestinal paediatrician, someone who deals with those issues in particular. I know that there are quite a few things that can affect the absorption of food, so its finding out what is causing it. Google is not your friend in this situation, its most important to get to a children's hospital or somewhere that they have access to different doctors and paediatricians who can help advise.

it must be scary for your friend.