The Link to iTunes and Link to iTunes if Modified statements support linking to iTunes via retained iTunes Permanent IDs (PIDs). These menu items are convenience functions to save or remove the PIDs. The functions always assume the PIDs are kept in a UDTI named iTunes PID.
The Save PIDs function only works on tracks which are linked and immediately unlinks the tracks. This is to prevent the inadvertent overwriting of iTunes metadata when saving the tracks. If that was your intent you can relink the tracks before doing a Save. The unlinking protects the scenario where you are dragging tracks from iTunes which have metadata in the iTunes library but little or none in the tracks.