I assume with "close" they meant that documentation should be located right there at the code it is documenting. Think Java doc comments (heredoc) or how in Golang you put comments above a function definition which is then automatically turned into documentation.
If documentation is located in an entirely different file, it's easy to modify code and forget to update the corresponding documentation.
Not only for foreigners. I needed an annual ticket only for a specific stretch to go to university, but there's no such option. Instead, I had to pay a ticket for travelling the entire canton.