It sounds gross but actually has a reasonable medical explanation as the article makes clear. Normally the donor is someone known to the patient, ideally someone living with the patient as they would consume the same foods but more importantly they would be acclimated to the same pathogens and any ailments of the donor would be a known risk factor. But in this case, the obvious questions is: Who is the donor and what health issues or prescription drugs are they on? There's a good chance the donors are employees that work for big pharma corps.
I think the duty of preserving gut pro-biotics falls to the appendix. It's an organ that had baffled mainstream medicine since its discovery but that would be because the concept of bacteria actually playing a healthy role in human health was generally foreign. But if someone gets a gastrointestinal bug that causes the body to completely cleanse itself through diarrhea, bacteria stored in the appendix repopulates the gut.
Those without them due to appendicitis & surgery do have a bigger challenge.