Operational issues with the scope of the source volume group
The Source Volume Group on the Choose Backups tab spans all steps of a Vault profile (most notably Duplication and Eject). However, if you do not duplicate images, you do not have to specify a source volume group (the field is ignored). Conversely, the field on the Duplication tab applies only to the Duplication step.
Even if no images are selected for duplication, images can still be ejected if they are in the Source Volume Group and in an off-site volume pool that is specified on the profile Eject tab.
See Operational issue with disk-only option on Duplication tab.