It was from a real early Wing Commander V treatment, but...
* Chris is right, the novelists didn't have any inside information on what Origin was planning. There would be an occasional meeting about a particular book, but nothing beyond that.
* It would have bee written well after the Wing Commander IV novelization anyway. The book was actually written while the game was being developed--which is why the authors only had access to the shooting script (when the game was delayed two months the book was pushed back on the publishing schedule and could't make it out until much later in the year... but it was done in December 95).
* The character's name in the early Prophecy drafts wasn't Lance Casey, it was "Tom Dane".