Binding to C++ is an extremely difficult and complex problem for any language that is similarly rich and has lots of (seemingly) equivalent features. The number of subtle incompatibilities and edge cases becomes nearly endless. It's not surprising that some C++ code can't be bound properly.
Yeah, that's what I realised. But I just wanted to mention that this is not what I was expecting from "excellent" interop. I would say that C has excellent interop, in general.