Exactly, also I believe the database in the music folder contains additional administrative content compared to the other databases.
I believe it’s the same kind of DB. I keep all my music on a d:\ folder. When I format my pc, I keep my partition, format c:\ and just reinstall engine. Everything works again 
I have noticed some differences, but i could be wrong.
eg
Smart Playlists info seems to be in default system “Music” drive ie C or if you changed it
Yes, that’s what I meant with additional administrative content.