Rob,
I think you are correct. We know relatively little about less common swords from Nepal. You have argued persuasively that your example has a strong Nepalese flavor. Perhaps we can agree that, until someone comes up with another similar example with a clear provenance, we have a presumptive attribution to Nepal for your example at this time.
A while back I wrote about the hansia, a work knife of Nepal and northern India. It is another with a curved blade sharpened on the concave edge, but th curvature is much more pronounced than your example.
Ian.