I believe that is designed by default to hide certain files so that the user might not delete them by mistake and damage the operating system thus rendering the PB unusable.
The demo video is considered "protected media" so it's inaccessible to the Samba (network) share.
The podcast episodes are stored in the Podcast app's own data area, so they would not be visible any way except possibly in a backup (including App Data) made using Desktop Manager. No app's own data area is visible to any other app or to the network share... part of the very tight security.