What are External Proptypes?

[Sparkette]

There's a private method on the Application class called Enable External Proptypes, that has a single Boolean "Enable" input. The description says "Enable or disable external G-based proptypes call". That sounds interesting; it makes me think perhaps it's another hidden, likely-buggy method for doing internal LabVIEW stuff in G, like XNodes/External Nodes, or External Editor Wizards (like the State Diagram Toolkit.) I'm pretty sure "proptypes" is an abbreviation referring to type propagation, so that could be fun to mess with. Anyone have any ideas?