This is likely just a hardware bug in your hard disk spinning up when libatasmart sends the IDENTIFY command. Most of my external hard disks works fine - only a single one exhibits this behavior. So there is little we can do about this. Closing (since I believe there is little we can do about this) and reassigning to libatasmart (since it is the component waking up the disk even when told not to).
This is likely just a hardware bug in your hard disk spinning up when libatasmart sends the IDENTIFY command. Most of my external hard disks works fine - only a single one exhibits this behavior. So there is little we can do about this. Closing (since I believe there is little we can do about this) and reassigning to libatasmart (since it is the component waking up the disk even when told not to).