I think of a playlist as an entity in its own right. Whilst I may have generated it from a directory or database query, I may then have manually edited it (removing that one track I always skip...).
Thus I'd expect resume to always follow the playlist, not to "recheck" with the place it came from. If I want to requery to get all-tracks-by-an-artist-including-that-one-I-just-added, then that's an easy enough thing to do. pondlife