Human stuff happens.
They are summarizing the ethnographers' experience. Given their position in a research world getting more and more hostile to naturalistic research in the behavioral sciences, they present their summary in terms used by those outside. Roger Sanjek offers a classificatory schemes for the kind of records which ethnographers have been known to bring back from their field trips and to find helpful. Many do not classify their records in this fashion, and few if any, come back with all types. I have cross-linked some of my own field records to point further to what Sanjek has in mind.