I was reading the below article and noticed the following paragraph,
Since that time, Air Force officials and Boeing executives have tried to make it seem as though they're acting in a frugal manner. The air force recently bought two Boeing 747-8s at a bargain price. That's what they say - they haven't revealed the cost, though, so it's hard to know.
Might the two frames be two of the undelivered whitetails that are/were previously stored? I read on this forum that the Air Force will want the frame for AF1 specially build with different cabling and electronics and a "stock" frame would not be adequate.
http://www.bbc.com/news/world-us-canada-41311526