The feed you linked is an Author feed and PowerPress does nothing to that feed. That feed is created by WordPress if you disable powerpress you will see the media files!
Note: Even if you removed PowerPress and placed media in a blog post WordPress is still going to put the media file in the rss feed. All PowerPress does is enhance your RSS feed so that it is podcast ready.. But Wordpress straight out of the box places media files in the rss feed.