the longer article is strange, because it suggests that the people in the myth know a lot of folks that we don’t know who they are (i.e. they are not in the story) and this resembles reality...
But I suspect that a lot of people listening to the Iliad or Beowulf would probably know who these folks are (their stories were lost). So the writer of the essay is probably wrong in saying this.
Modern novels don’t tend to put someone unknown in the story, however, because that is the modern “rule”.
However, the criticism breaks down for Lord of the Rings, because Tolkien’s books are full of characters who we don’t know who they are or what he’s talking about (unless you read the 14 volume collected works)...
I am reading Game of Thrones, and the author must not have learned the rule about not mentioning extraneous people. As each chapter starts, I cannot usually remember if we are talking about someone we have already met, and whose story I should know, or if it is someone brand new. It is becoming exhausting, and turning into a reading slog. Lord of the Rings, and even The Silmarillion, are the souls of brevity in comparison ;)