Outbound Contact List 409 Conflict during Terraform Apply

General Discussion
1

Could someone explain why pushing a contact list with duplicate external IDs causes a 409 Conflict instead of upserting?

Environment: AU-1 BYOC
Provider: genesyscloud v1.22.0

resource "genesyscloud_outbound_contactlist" "example" {
 name = "Test List"
 description = "Duplicate check"
 # External IDs are unique in source but fail here
}

Terraform expects idempotency. API rejects the second apply. Need to know if manual deduplication is required before push or if there is a flag to handle this.