Their claim is that editing by subtraction creates a more efficient story, but not necessarily a better one. These editors say that if what the story needs is another scene to make it better, then that is what must be suggested. The relationships between the editors and authors is also important in the publishing of their stories. The majority of authors are very cooperative. They listen to the editor's suggestions, and respond in a generous manner.
Most writers are open to suggestions and change.
Most editors are also very cooperative as well. If an author disagrees with an editor's suggestion, most editors will go back and reconsider their suggestion. There is a minority of authors that are more resistant to change. This happens when the author and writer's views on the story are completely different, when they disagree as to what the story is trying to say, and how the story should go about saying it. This willingness to cooperate has nothing to do with track record.