I was told by Timo who works at Kemper that this is not so
Amps and Cabs are embedded in the Rig. Deleting the Rig means loosing the content incl. the Amp and/or Cab.
Timo was making a general statement. In your case (fav with cab from another rig) you are not deleting the rig in question (the fav), but a rig that happens to have the same cabinet. both are separate entities.