Hi Mike, it's because Modo is writing polygon mesh geometry to the 3DM file and not NURBS objects.

There are numerous different kinds of things that can be stored in 3DM files, like polygon meshes, NURBS solids, curves, annotation text, dimensions, spotlights, etc....

Of all those kinds of things MoI is only focused on dealing with NURBS data, it does not read in other kinds of data types like polygon mesh data.

If you want to work with polygon mesh data, you will need to load that data into a polygon mesh editing program and not into MoI - MoI is specifically focused on working with NURBS data at modeling time. You can export polygon mesh data out from MoI but not read it back in again.

- Michael