This question has been answered by sottwell. See the first response.
GetResources by its nature does not deal with levels as such, it creates a single flat output. Perhaps you would be better off using Wayfinder, or even better pdoMenu to create your structured output.
While by default pdoMenu (and Wayfinder) creates a simple nested unordered list, you can use tpls for each section of the output to form any structure you want.