Don Evans' "The United States 1c Franklin 1861-1967" book discusses misperfs on this issue in his section on varieties and production errors, pp34-38, citing the double perforation as the most common error, since perforating was done manually. Add to that the photo comparison above, I would start with the premise that you have a production error, rather than some later fakery.
Here is a #65 with double perfs cropped from a cover.
