Again I have to complement you for coming up with examples that might seem to be single scans, but I don't think the stuff from Google qualifies.
I didn't see any pictures on page 89 of the book, but I looked at the image you offered. The lines at the bottom are simply not from a scan. They are all a uniform black (RGB=0,0,0) and are not a product of a scan. Maybe they are some frame that Google added? I don't know. As I said I didn't see the source for this.
And it doesn't matter. I did Google =google books scanning technology= . It's pretty clear that Google has their own proprietary system. This isn't something that would be necessary or available for scanning any document received from Hawaii and in fact nothing similar happened in the other pdf the White House released at the same time.
ML/NJ
The image I posted came from page 89 of the PDF file, not the book. The solid black portion is actually part of the illustration, not a frame added later, so it's unlikely that they went in later and added random parts of a picture.
I'm not sure why you still think uniform black pixels are evidence that they are not the product of a scan rather than the product of a well-documented process that enhances elements of the source material.