I am looking at a scenario in which my SolidWorks assembly uses a Creo subassembly, and that Creo subassembly uses a SolidWorks part.  The SolidWorks part was added to the Creo subassembly using PTC's UNITE feature (without the EFX extension).  So it is not converted to a native Creo part, but is instead recognized as a SolidWorks part, within the Creo session:

When I add that Creo subassembly to my SolidWorks assembly, no errors are displayed, and the SW model tree looks correct.  However, the SolidWorks component of the Creo assembly is not shown in the graphics window:

I assume this is because once SolidWorks opens a subassembly from a different CAD tool, it expects all children of the subassembly to be in the same format.  Is this assumption correct, or is this hybrid kind of MultiCAD scenario expected to work?