The Kendo UI Toolbar widget supports enabling/disabling items via the various enable options for items, splitButtons and buttonGroups or after initialization via the enable() method. In this DOJO, I have created a toolbar with a splitButton that contains several sub-items. As you can see, I have disabled the second sub-item via the options.
However, after disabling and enabling the whole splitButton, the second sub-item is no longer disabled and can be used normally although its enabled property has never been touched.
Since the "main" item of a splitButton is an item on its own that a dedicated click-action can be assigned to etc., I would not expect the enabled property to effect its sub-items.