The first three chapters are about how you work. This one is about the thing itself. An application is a small number of parts that always show up: something the user sees, something that runs on a server, somewhere the data lives, a way to tell who is logged in, and a handful of other companies' services doing the work you did not want to build.
You can direct an AI to write all of it without knowing any of this. What you cannot do is decide. Which part should hold this data, whether that key is safe where you just put it, why the page broke, whether the fix an assistant just proposed is a fix or a hole. Seven sections, each one aimed at a decision you will have to make.