It turns out I was misinterpreting what I was seeing. The documents weren't shrunk, but were universally smaller than the scanning platen sized for 8.5" by 11" "Letter" sized paper. That's because back in 1921 two different Federal committees came up with two different paper standards .
Not until World War I or shortly after was a standard paper size agreed to in the United States. Interestingly enough, within six months of each other, two different paper sizes were set as the standard; one for the government and one for the rest of us.
1. In 1921, the first director of the Bureau of the Budget established an interagency advisory group with the President's approval called the Permanent Conference on Printing which established the 8" x 10½" as the general U.S. government letterhead standard. This extended an earlier establishment made by the former President Hoover, the Secretary of Commerce at the time, who established the 8" x 10½" as the standard letterhead size for his department.
2. Now, during the same year, a Committee on the Simplification of Paper Sizes consisting of printing industry representatives was appointed to work with the Bureau of Standards as part of Hoover's program for the Elimination of Waste in Industry. This group came up with basic sizes for all types of printing and writing papers. The size for "letter" was a 17" x 22" sheet while the "legal" size was 17" x 28" sheet. The later known U.S. letter format was these sizes halved (8 ½" x 11" and 8 ½" by 14").
I vaguely recall coming across the idea of a minuscule size difference between "government" paper and regular paper before, but I wrote it off as an urban legend or waggish commentary on government efficiency. Personally, I'm not going to get too bent out of shape that my few reproductions of Federal paper are slightly oversized. It's a legitimate concern for anyone worried about the absolute authenticity of prop documents in the classic era. For casual game use the hassle of resizing document templates and hand trimming paper to size is too much effort for too little reward.