A big problem with calling revival singers "traditional singers" is that it falsely implies that the revivalists' words, music, style, instrumentation, and performance truly represent those of actual traditional communities. But by definition they do not.

A serious related problem is that loose terminology can lead the unwary into studying revival versions for insights into the distant past. For genuine insight they need to go back instead to actual traditional source singers, who usually sang unaccompanied and without "showmanship."

As Steve suggests, some revivalists - including Barrand and Roberts -   are excellent artistic *interpreters* of earlier material for modern audiences. At best they sing authentic texts to authentic tunes (though not always collected from the same person!). They can also convey the emotion of the songs without resorting to pop music tricks, dynamics, rewritten lyrics, etc.

Even the most pop-oriented performers can make worthwhile music for fans devoted to current singing styles. (Celtic Woman is my favorite example.) But they aren't "traditional" singers, and what they do has little enough to do with "folksong."

For Celtic Woman at the top of their form, try this:

https://www.youtube.com/watch?v=vI_TV32jmHc

Beautiful but not very "traditional."