Shankspatel, I will say again here there is a good probability there is no extensive damage to engine. Unless the engine is running on high revs for a long highway run putting extensive load and coolant around the engine when totally drained. I believe diesels take some more abuse for engine to seize or develop trouble. SA will suggest this to be on safer side. He is trained to do so, to avoid future problems with customer. (like prior counseling). However fix radiator and fan asap, or tow the vehicle for repairs if radiator and fan is badly damaged. A leaking radiator and full damaged radiator is different.