Models With 7.4 Extension Properties Are Not Being Decorated

The default behavior is that if the model is storing any of the registered Model Extension Definitions (MEDs) than the model is decorated with the extension model overlay. But the 7.4 models with extension properties do not have a MED stored in them. The DeprecatedModelExtensionAssistant needs to override the superclass functionality and check a model's model objects to see if any have 7.4 properties.