@pcmoor said:

A component file is created via the right click menu "saveas"

If you open this file you see its contents not the parent, so saving leaves a parent with the groups as per your file,

You need to import the file as done and explode then via right click "saveas" to overwrite or drag and drop. then the parent data is destroyed

thank you very much pcmoor. I suspected there must be 'parent data' buried in the file somewhere - I just couldn't figure out where it lives or how to access and then delete it.

And I was not aware of the 'best practices' of saving a component to disk via the select - right-click - Save As operations. I have always just saved a model to disk with the File -> Save As... option - without first making the model a component - and then relied on the File -> Import... into my larger model to turn that model into a component. I shall make better use of the component -> Save As... operation.