If you need to archive data from multiple mount points, e.g. both M:\ and N:\DataForM\, it is considered best practice to select both paths for backup.
The Archiving task scans all mount points by design, and if stub files are encountered on a mount point path that is not part of the backup selection, the service will start rehydrating these stubs even though they are backed up on the other path (i.e. the path included in the backup selection).
To avoid inadvertent rehydration, include both mount point paths in the backup selection.