I would ask Vadim Rozenfeld for more info

Also the bug doesn't contain enough information to see exactly where the problem is w/in the existing documentation.

I am wondering if the title should be changed, to reflect that it is a Windows installation?  I changed it, but if I am incorrect, pls change it back....

Sure, it is not possible to update IDE device with viostor driver. They are just incompatible, and Windows installer will refuse to do it, no matter how hard we try. If we are taking this scenario, then you are absolutely right - the docs are really misleading. 
But I believe, they are talking about different situation: 
- a system (VM) has no viostor driver pre-installed; 
- a new virtio-blk device has been recently added to the system;
- on startup Windows recognized a new storage device plugged in;
- Windows PnP manager failed to find a device driver, which matches the new HW
  and installed a stub "SCSI controller" driver and put it under "Other devices"
  category;
In this case we do "update" driver. But we update a stub with a real driver.
Actually the same situation happens with the rest of out drivers - net, balloon and serial. Windows recognizes PCI class IDs and puts devices under predefined category, according to these ids.

So, we are not updating in-box drivers, which are running on top of emulated devices with our para-virtualized drivers. We update default (stub) drivers,
installed by Windows, with our functional device drivers.

Best,
Vadim.