Hi, I am currently using the instant-on power mode, and noticed that in this mode the HDD is ALWAYS running. It doesn't stop or spin down at all. You can check by your own simply by approaching the ear, you can hear a periodic "clac, clac, clac...".
I think while it is not downloading anything there is no need to keep HDD spinning, for saving energy and HDD mechanical parts.
Please revise this and fix it with an update.