I have a 3TB Western Digital external "conventional" drive, and haven't noticed any sleep problems.
As near as I can tell/summarize, the "problem" manifests itself if your display is set to sleep, and you have secondary internal or external platter drives. The drives (at least on the systems reporting the problem) are following the display sleep setting and sleeping when the display does (actually about a minute after). If you set your display sleep to "off", then the drives do not sleep (regardless of any pmset disksleep setting).
This can wreak some havoc if one has parts of the OS (such as your home folder) on a sleepy secondary drive, at the least a beachball when accessed. It can be an annoyance for apps accessing those drives (delay), though at least CCC seems intelligent about waking up a sleeping drive to back up to. My nightly CCC job now logs a 4 second delay before copying that wasn't present prior to 10.8.5.