If there are podcast hosts who don't hold onto their original audio files they had before uploading them, then what are they thinking? That's like sending a project to a client and then deleting your own copy of it.
I understand that the author tries to provide an "import from Apple Podcasts" service for convenience, but that's merely a convenience. It really shouldn't be too hard for a podcaster to just re-upload their original audio files and descriptions to a new service. Nobody's "locked in" to anything here as far as I can tell.