It's up to the person doing the dummy to decide what they want to do.
That said, I always include everything that I want in the book. Cover is definitely there, and if I envision endpapers, I include them as well (not every book has end papers, but they seem to be more common now than they used to be).
Are those pages necessary? Maybe. Maybe not. But I always include what is necessary for me as an author/illustrator to tell the story.