However, if the MIDI file in the List Browser is then dragged to a track doesn’t that create a link from the List to the Arrangement?
No. The MIDI file gets imported as a sequence of notes, all contained within the Podium project file. Sound objects are linked to their external file because the wave data are not embedded in the project file.
If that is not the case at present, could it be in a future development
It could be, but that’s a long way down the road.