This only happens after the first time a slot has been loaded with a rig then changed to a different rig.
The slots name info was empty before the first Rig was loaded, then the slot used the Rig to add a name info
after that this name info will not be automatically changed when you load a new Rig.
If you were to name each slot say intro, verse, chorus, bridge........ then no matter what rig you chose for the slot it will keep this slot name.
Its not a Bug, just not Obvious to the user that this Info needs to be set by the user one time per performance.