The critical case against the collection is specific rather than general, and the atlas records it in full because the material cannot be assessed without it. First, contamination: in most cases the two families had met before the investigator arrived, so a child statements were recorded after there was an opportunity for the child to have heard the details, and reconstructing what was said beforehand depends on the memory of people who now have a stake in the answer. Second, the interpreter. In much of the fieldwork the person translating was also the person who had located the case and knew what the answer was supposed to be, which is exactly the arrangement that controlled testing exists to prevent. Third, selection: a child produces many statements and only some correspond to a real person, and deciding which count as hits is a judgement made after the match has been proposed.
The answers offered on the other side are that the birthmark cases carry independent physical evidence, that some cases were written down first, and that the sheer volume is not explained by any one mechanism. Neither side has persuaded the other, and the honest description of the situation is that it has never been resolved rather than that it has been settled in either direction.