If you want your posts and pages to have different layouts, you do not need to customize each and every page/post. You will simply customize 2 layouts and then rely on layout inheritance.
In the layout selector, choose the Single layout and build the layout that you want all posts to use. Note: You can also build it as a Shared Layout and apply that to the Single layout.
Make sure you save it! Then, edit the Single » Page layout
Build the layout you want and save. Now, ALL posts will use the Single layout and all Pages will use the Single » Page layout. Easy, right?
Note: Any posts or pages you’ve customized indvidually will use that layout instead of inheriting the respective layout.
Then, can you tell me what’;s the purpose of the Single>Post template? If Single represents the Post, then isn’t Single>Post redundant?
Single doesn’t represent the layout for the Posts always. Single represents the single layout for: single posts, single post types, pages if you only customize Single.
So in this tutorial: You could switch it around and customize Single > Post and then customize Single to represent the layout you want for the pages.
OR You could customize Single > Post and Single > Page and do nothing with Single.
OR You could customize Single > Post and Single > Page and then customize Single for all other single post types.