@MAM59
What do you mean with "seperate settings"?
I have like the same issue but my WD my Book are going well in standby because of the controller on the case.
I did it with the regular software "WD Drive Utilitys" and have set the spin down to 10 minutes.
But i have the issue every 15 minutes the unnassigned WD drive awakes for no reason (not even mounted etc.).
I'm actually troubleshooting this but maybe i have to open a new case here.
The same model on my windows host, stays in standby.
Thats why i think something in unraid is awaking the device for some reason.
But the syslog is quiet at the moment when the USB drive spinns up, so i have no clue where to start to troubleshoot this issue.
After all when this HUB spinns down, in unraid it is still marked as online (green LED) but im pretty sure out of the noise and energy consumption it has spin down.
I can clarify this by screenshots etc.
Maybe someone have the same issue and can help me out?