Terraform 422 on Predictive Routing Outbound Campaign

How should I properly to handle the genesyscloud_routing_outbound_campaign resource when the API rejects the config with a 422 error during terraform apply?

Running in AU-1 BYOC with provider genesyscloud v1.68.4.
The deployment pipeline uses GitHub Actions to push state changes.

The HCL block looks valid:

resource "genesyscloud_routing_outbound_campaign" "test_campaign" {
 name = "Test Predictive Campaign"
 description = "Managed by Terraform"
 enabled = true
 
 calling_view_id = var.calling_view_id
 
 rule {
 name = "Default Rule"
 # ... other rule config
 }
}

Error log:
Error: PUT /api/v2/routing/outbound/campaigns: 422 Unprocessable Entity

The response body mentions:
"message": "Validation failed for field 'rule'. Invalid rule configuration for predictive mode."

I have verified the calling_view_id exists and is active. The rule configuration matches the JSON schema returned by a manual GET request on a working campaign. Yet Terraform refuses to apply the resource.

Is there a specific attribute missing in the HCL that is required for Predictive Routing but not documented? Or is this a known limitation with the current provider version in the BYOC region?