Of course, my c.v. does include traditionally published books, but in those cases, I was hired (yes, on a freelance basis, which you would not “count”) by the publisher rather than by the author. The reason my marketing to authors instead emphasizes my experience with self-published and even vanity press authors is because working with a publisher is different from working directly with an author, particularly with an author who has made a conscious choice not to be traditionally published. Some might even say that working within a publishing house provides less preparation for working with self-published authors than does working with other self-published authors. I, however, would not go so far as to say that, because I really do believe we can come to our profession by different paths, just as people can come to writing by different paths.
Obviously there is a big difference. I actually started with screenplays (with some mild success) partly due to hearing that as long as you have a good story, the grammatical errors won’t be a big deal. Well, that was not true. Maybe if a producer liked the story or I was already established but every contest I entered always came back with feedback about the grammatical errors. Even if I won or placed as a finalist, I always received critique on that. Very little is spelling error, it was more about structure, etc.