When using the UnAssign window, you are presented with several possibilities:
- Unassign one material from some selected entities.
- Unassign one material from all the entities that may have this assigned.
- Unassign all materials from all the entities that may have them assigned.
When using the command line, UnAssign works as the third option here, i.e. all materials. For only one material, use UnAssignMat (see Assign material).