Yes, the DHL Shipment Tracking - Unified API will first lookup in its sources for a shipment ID with the provided string; if not found, it will then proceed to look up the value as a Shipment ID category; if it finds a match, it will show the history of the related shipment.
For example, you could input the code "JND00000000000000001" in the tracking ID. This is a fictitious number of a Piece ID of a shipment from DHL Global Forwarding & Freight (DGFF), but it's not the shipment ID. Then, the Shipment Tracking - Unified API will show in the body response first the ID of the shipment, which is AAA-BB-123456 (also fictitious), and then the tracking history of the shipment.