When SingleSelection is false, the user's context-click on a selected object does not modify the selection, thereby allowing the context-click action to apply to a multiple selection.
If the user holds down the Control and/or Shift keys, or when SingleSelection is true, the standard GoTool.DoSelect behavior occurs. When the user context-clicks over an object that is not selected, it becomes the single selection. When the user context-clicks over no object, the selection is cleared.