There are people who use the term "animal" to refer to "mammals".

If they were argumentative about such things, in the Mudcat tradition, I suppose they wouldl tear into each other about what to call duck-billed platypuses, frogs and caterpillars so as to distinguish them from oak trees and mushrooms.

The varieties of folk music around the world are far far wider than the particular types of music that tend to be given that label around here - and musically they do not have that much in common. What they have in common is stuff like the kind of social situations in which they have developed, and the kind of people who make the music and make use of it for social interaction of various sorts.