USB hard drive doesn't graceful power off after eject on Windows 7

I have a couple of Seagate FreeAgent Go external USB hard drives and would like them to gracefully power off after ejecting in Windows 7.

With Windows XP a few seconds after they are ejected they gracefully power off. When ejecting them on Windows 7 they just stay on and have to be physically disconnected before they lose power.

I have checked the hard drive removal policy and it is set to quick removal. I have also looked in the Seagate forums but I couldn't find any info on this so I thought I'd ask the SuperUser community on any ideas why the difference and how to get the same behaviour in Windows 7 as in XP?

Update: I am finding that this also happens with USB thumb drives as well.

My current theory is that there were changes to the driver model with Vista/Win 7 that haven't been reflected in the device drivers yet. So things that worked under XP don't under Win7 as the drivers haven't been updated for the new model. Does that sound right?

I believe that this a new "feature" in Windows 7, and the problem is with all USB disks, nor just with FreeAgent.

See also this thread for the same thing with other manufacturers.

EDIT: Microsoft now explains this feature and how to undo it in this article :
USB Port Remains Active for Disabled or Safely Removed USB Device.

This can be done per-device. I reproduce here the global setting for all devices, which is in registry key
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\usbhub\HubG,
new item DisableOnSoftRemove (DWORD), data value 1.