This behavior is by design - in case the TargetControls collection of the RadToolTipManager is empty, the manager tooltipifies all elements on the page that have a Title/ToolTip attribute. In case you do not want to use this feature, you should set the Visible
property of the manager to false, when that collection is empty, and set it back to true as soon as you add IDs to it.
All the best,
the Telerik team