In old times projects using gtk-doc had a template files to have the skeleton of the documentation. These days most of them (like clutter and gtk+) don't use them anymore.

In general I feel that the documentation structure on both gtk+ and clutter are cleaner. For example, right now the documentation of atk signals and the description of each object (SECTIONS) are written on those templated documents, but the documenation of atk properties and methods are written at the source code. It would be cleaner to have just one place (.s source file) to write the API reference, and keep the fillers at atk/doc to explain the high level purpose of the library, or specific documentation, like the hypothetical guidelines.