Folks:

I think the word that summarizes what Winegardner did is 'redaction' - here is a definition:

Redaction
The process of revising a work so as to weave in themes and ideas that invest the finished product with themes and emphases the redactor wishes to emphasize.

This word is typically associated with theology in terms of critically analyzing the historicity of the Bible. While the Godfather is not equivalent to the Bible, I think that we can safely say that Winegardner has redacted what was publicly accepted as cannon.

To that extent, I think that we should view GFR not as 'gospel' but as 'pseudographia'.