Bug? MarkupObjects Tag Property

All of the Markup objects have a Tag property that (according to the Object Browser) is a Variant data type. However, when I try to set the Tag property to an object variable (a VB6 class), the Tag property value is Null. I think this is a bug because regular Variant types can hold object references. 

Any chance that the Tag property can be extended to support regular VB6 classes (or another property could be added that could support them)? It would be useful for appending additional arbitrary information to objects, rather than having to keep a separate collection around for this purpose. Other controls that I use support this kind of thing, and it is useful for extending the information related to object/controls.