Yes, I read it, but, no references and I've always seen it mentioned as grain shear stress when I've come across it in sedimentary/marine geology.
The text is about submarine sediments. Sediments are made of grains of differing sizes from clays, through silts and sands up to pebbles (eventually boulders). Because of this, I wouldn't have any problem referring to it as a grain shear stress. I guess if the intended audience is not one of geologists, sedimentologists, geotechnical engineers and the like, then skin friction shear stress might be preferred. As I've remarked, both are widely used in the literature.
Have a look at figure 73 of
http://theses.univ-lyon2.fr/documents/getpart.php?id=lyon2.2... and compare it with figure 8 on page 24 of
http://lvov.weizmann.ac.il/lvov/Literature-Online/Literature... . The text refers to the same thing (the French is based on Zhou Liu's original), but the choice of terms differs - both are equally valid.