Here's a problem. I learned an old blues from my step-father. I recorded it. I have not heard it sung anywhere else ever. In this way, I am a traditional singer because it was passed down to me through my family. I even sing it in the style in which it was taught to me. I learned it as a young child.

The folk songs I have learned in a way that would classify me as a revivalist, not a traditionalist. Could I be both?

When Doc Watson records "Over The Rainbow" is he still a traditional singer? I think that
because of his background he is. But if he sings and records Harold Arlen/Yip Harburg is he a kind of "revivalist" singer too?

I'd say, here, Doc was both. A traditional singer and a non-traditional singer.

Or when he sings a non-traditional song, he is a non-trad singer and vice versa.

The whole point about defining what is a traditional singer is this, honoring the tradition or culture and the people who came from where the song was originally done. It's not about splitting hairs over definitions but an attempt to understand and elevate the folksong tradition by acknowledging the sources for the songs.

Lonnie Donegan, for example, was not Leadbelly, who reflected a given tradition of the isolation of the African-American singers on chain gangs..

One could argue about Burl Ives, however. Or Josh White. They had traditional roots.