I saw this on CNN today.

For months, US intelligence and military personnel in Iraq have been raising alarms about the risk to American forces from these newer, more sophisticated Iranian-made drones. Rather than being guided by a pilot from a remote location, some of these small, fixed-wing drones use GPS navigation, making them far less visible to US surveillance systems and impervious to jamming.

I understand how an independent guidance system is probably jam-proof, but how does using GPS make the drones less visible? Don't all military drones rely on GPS?