From the abstract at Amazon:
Today’s popularity of easy-fitting styles and knitted fabrics means that basic ‘flat’ pattern cutting is used to construct the majority of children’s wear and babywear and this type of cutting is therefore emphasized in this new edition. Shaped blocks and garments, cut to fit the body form, are still included, and are placed in chapters covering some school uniform garments or more expensive fashion or formal clothes.
One primary difference between flat versus fitted pattern making is that the patterns have the same shape for the front and back pieces. For example, the armhole shaping is symmetrical. Creating patterns in this way results in a looser, more casual fit and it is appropriate for a lot of children's clothing. Even so, I see more of a modified flat method in actual use. Patterns are modified so that they aren't quite so boxy and more fitted. Yet, they retain some symmetry between front and back pieces.
I'm sorry, I don't have any pictures to show the difference, but if you have the 3rd edition, you will see examples of the flat versus fitted method. I don't yet own the 4th edition, but I do think I will eventually buy it. The book does include a section on plus-size children. I think that is a first for a pattern making book. I am sure the book is up to it's usual standard and would be a good edition to a DE's library.