Somewhat odd for the Appalachians

If by this, Jim, you mean that it was odd he met only two black singers in an area with a large African-American population, that can be explained partly because he looked for (or was directed to) areas where people were known to sing the old ballads, which in practice meant areas with a high proportion of British Isles descendents. On one occasion that we know about, he and Maud Karpeles turned back from a particular township when they found it had a mostly black population. There was a lot of segregation in the mountains at the time, so for instance the rather isolated rural community of Madison Co., NC, where they got a lot of songs on their first trip, had only a tiny black component.