Do these authors believe in the reality of miracles, such as at Lordes, Guatalupe, or in the Gospels? If not, then they are just atheists or pagans operating under the label of Catholic.
IIRC, they began their research expecting to retain their RC ‘orthodox’ perspective on things.
I don’t recall specifically what they thought of other such, if they said. They may have said something neutral to positive in their preface but I just don’t recall, for sure.