It seems to be possible to import Parts and Hardware on a product level using XML importing but appears to only work when the imported product name doesn't match any existing products in the library. Is it possible to import a product with parts, hardware, and subassemblies into a product that already exists in the library and just append them to any other existing line items?

I've attached an older sample XML importing file that used to be apart of the XML Import article that shows parts and hardware being included with a custom product.