Back in my USAF days, cannibalizing parts from one aircraft to another (we called it "cannonball") was sometimes done, however generally discouraged and required some approvals.
That said, having a complete, flight ready A/C as a donor would support mission readiness.
I interpret the article saying these 8’s are a flying part of the AF1 fleet. As I stated above this may be the step that knocks out the Boeing order which seems like will not happen anyway.