ProvisioningTargets are passed the instantiated backend configuration (eg: FileProvisioner) via provision(), but ExternalIdentitySources are passed the parent configuration (ExternalIdentitySources) with the backend configuration retrieved as a related model (eg: $source->file_sources). The latter is probably better, in case the plugin needs to know the parent configuration for some reason, but one way or another standardize this and check to see if other types of plugins have the same issue to resolve.