In the Tycho documentation the "simple target platform configuration" is the first entry for "Target platform configuration":
<repository>
<id>eclipse-indigo</id>
<url>http://download.eclipse.org/releases/indigo</url>
<layout>p2</layout>
</repository>
Let's assume that's because it's the default way for setting a target platform, an assumption supported by the fact that the Eclipse guys seem to do it that way.
How do you develop against a module with a target platform set that way? Normally you'd have a "*.target" file somewhere and set it, then start your tests / product / whatever.
Not sure why the 'simple target platform configuration' is mentioned first. Even though it might be the simplest form to set up, it is of limited use for real-world use cases.
Most Eclipse projects I know of which consume Eclipse platform bundles use target platform definitions, both within the IDE and in their Tycho build.
If you are using a target platform definition in your IDE (.target file), you should also instruct Tycho to use that target platform (see also 'Which approach shall I use for the target platform of my project?').
This way, you only need to maintain a single source of dependencies. Furthermore, you can define different target platform definitions and thus verify that your code works well across different versions of the same target platform.
With a simple target platform configuration you would need to manually keep the target platform of the IDE in sync with the Tycho target platform.
The 'Target files' section of the above wiki page explains the details and differences to the IDE
Does that answer your question?