javascript - Bookshelf.jsモデルを取得する際の「新規」使用の違いは何ですか?

Question

Bookshelf.js ドキュメントには、「new」を含むコード例と「new」を含まないコード例があります。

ここhttp://bookshelfjs.org/#Model-instance-hasMany

let Author = bookshelf.Model.extend({
  tableName: 'authors',
  books: function() {
    return this.hasMany(Book);
  }
});

// select * from `authors` where id = 1
// select * from `books` where author_id = 1
Author.where({id: 1}).fetch({withRelated: ['books']}).then(function(author) {
  console.log(JSON.stringify(author.related('books')));
});

しかし、ここhttp://bookshelfjs.org/#Model-instance-fetch

let Book = bookshelf.Model.extend({
  tableName: 'books',
  editions: function() {
    return this.hasMany(Edition);
  },
  chapters: function{
    return this.hasMany(Chapter);
  },
  genre: function() {
    return this.belongsTo(Genre);
  }
})

new Book({'ISBN-13': '9780440180296'}).fetch({
  withRelated: [
    'genre', 'editions',
    { chapters: function(query) { query.orderBy('chapter_number'); }}
  ]
}).then(function(book) {
  console.log(book.related('genre').toJSON());
  console.log(book.related('editions').toJSON());
  console.log(book.toJSON());
});

違いは何ですか？