NIS 22 Optimization Settings - Yes and No at Same Time?

Just upgraded to NIS 22 a few days ago.  I see the usual On/Off setting for Idle Time Optimizer in Settings/Administrative Settings.  But now there is an apparently independent setting for Disk Optimization in the new (or did I just fail to notice it in v22?) Settings/Task Scheduling/Automatic Tasks section.  Aren't these both for idle-time defragmentation? *Is* there some difference between the two? What happens if one is enabled and the other is disabled?