When a service request is created /edited, a check is conducted on the value of the setting “Do not assign technician before service request is approved”. If this option is disabled, Technician Auto Assign will be applied to the service request based on the configuration. And, if the option is enabled, then Technician Auto Assign is applied after the service request is approved.
When Technician Auto Assign is applied to the approved service request, the operation is considered as Edit, so the technician is applied only to unassigned service request.
Unassigned service requests denote the requests that are not assigned to technicians even after the application of Business rules, category or default technician from the UI.