Why don't Stitcher and Tune-In appear in Podcast Clients?
Unfortunately there are a bunch of podcast services/apps that do not send their subscriber data with their user agent, nor are all user agents (Podcast Clients), a human being. Some are just robots, scanning the Internet for things to download.
Stitcher and Tune-In can be tracked for podcast downloads, but they will not show up in Podcast Clients. According to Stitcher, they're trying to emulate iTunes for download data, and if Stitcher pings your FeedPress feed, we can give you the download analytics without issue.