Because the Picker is not part of the Plugin to have all tracks info, you are just opening Biab (BBW4) in the background, it's not part of the Plugin. BBW4 just renders the track/s to wav in the SavedTracks folder then the Plugin will play them and drag in the DAW.
If you want all the Biab main app functions you are best to just drag the wav into the DAW from Biab main app or use the Rewire VST or Import SGU Reaper,
or wait until they get all the generate code into the JUCE Plugin.