Views Data Export Module not including the custom added rows in a view
Views Data Export does not render your results in a traditional way, so render hooks are not executed. But you should be able to alter results using hook_views_post_execute:

This hook is called right after the execute process. The query has been executed, but the pre_render() phase has not yet happened for handlers.
Adding output to the view can be accomplished by placing text on $view-&gt;attachment_before and $view-&gt;attachment_after. Altering the content can be achieved by editing the items of $view-&gt;result.

Emphasis mine - that's what you should to to alter content not only for display purposes, but in generic, usage-independent way.