From http://help.autodesk.com/view/INVNTOR/2018/ENU/?guid=GUID-6A540540-CA8A-40AD-8EBF-C4BB1F3E7288
"An object proxy is a reference to an object through a particular occurrence. Think of it as a pairing with its respective native object, but returns context-specific data.
An example is a face of a part within an assembly. When this face is queried through the API, what do the results mean - are coordinates returned in the context of the assembly, or the native part? What if the part is inserted into the assembly multiple times; how is a particular instance of the face identified? A key purpose of proxies is to provide answers to these questions. In this case, the proxy of the face object performs the necessary transformations to provide point data in the required context, and also provides information about which occurrence the face is associated with."
So for your question the ObjectTypeEnum are telling you if the object is a proxy object or the actual object.
