Wouldn’t a mono space font provide more information since you can extrapolate the exact number of characters?

My guess is that is actually less information than you get from a variable width font.

Either way, fixed or with index lines.

This is the government. The documents are faxed/photo-copied/etc etc. They are a bunch of random docs from random sources and the original creators never thought 'This will be redacted'. They just fired up word and started typing.