Perhaps this will help...
When you are managing files with MC and have a local Library in use, you can Send files to your SBs. These will be streamed files, w/out meta-data. You'll see only something such as http://.../something.* (where * might be mp3, flac, etc. depending upon transcoding options).
When you instead Library Manager->Connect to Library...->DLNA Media Server and select the SB's library (by Whitebear), MC creates a new DLNA Library. It takes a while to import the meta-data. Once done, you can now play audio files and the meta data will appear.
Note that MC allows you to be working with only one Library at a time, so you'll have to chose at any given time how you want to send your music to your SBs. Just switch which Library you are using to see which one suits your needs.