I'd expect the old session directory to become expendable where a user took the action to specify a new location on the filesystem to be used to persist session data.
your expectations are not confirmed and never will I'm afraid... changing the session directory does NOT move any existing files into the new directory--they stay where they ever was, in the old directory.
the new directory will the location where NEWER files will be created (eg. new clips, new recordings, etc.)
and yes, automation curve .mid files may seem an exception but in reality they are just recreated on every save, so probably the new versions, whether modified or not, are always (re-)written to the new directory.
your expectations are not confirmed and never will I'm afraid... changing the session directory does NOT move any existing files into the new directory--they stay where they ever was, in the old directory.
the new directory will the location where NEWER files will be created (eg. new clips, new recordings, etc.)
and yes, automation curve .mid files may seem an exception but in reality they are just recreated on every save, so probably the new versions, whether modified or not, are always (re-)written to the new directory.
hth.