This criticism is potentiallyvalid given the fact that the term Nutritionist or Nutritional Therapist (NT) is not yet a legally regulated title in Ireland (or the UK) therefore anyone could conceivably call themselves an NT without breaking any law.
In fact, in a very contrite reply to a comment on their paper, they not only agreed with the commenter that his criticism was potentiallyvalid but they pointed out that there were other even more important deficiencies in their model.