In power manager settings "Put the computer to sleep when inactive for" appears. It is not clear whether this means suspend or hibernate (suspend and hibernate being the two actions in the drop downs). It would be nice if the language was consistent with the drop downs (eg. "Suspend when inactive for"). I suspect that in this case sleep means suspend to ram - does this mean there is no way to automatically hibernate after a period of inactivity? I guess that could also be considered a bug.
This combobox has now (version 1.3.1) been split up and moved into the same table that holds the "Put system to sleep when inactive for", making the meaning of the "sleep mode" more obvious. Depending on the policies your distribution set you can either choose hibernate, suspend or both. So yeah, the system sleep mode does allow you to hibernate after a period of inactivity (if your system allows it).