In his defence the OP asked if the IDG oil temp sensor could be changed seperately and you went into detail of the fuel temp system and engine oil system
As regards to your question then I suppose it does have external temp probes, remember oil is being circulated at many points through the engine hence the oil temp is not taken from the IDG itself.
As the engine oil and IDG oil don't mix in the fuel oil cooler i'm not really sure what point he's missed exactly.
Back to the original question, we can't change the temp sensor seperately on ours either
