Did you read the whole article? Either the author is wrong, or you and I are miscommunicating.
Letter spacing will remain constant, even in a low-res scan. The fact that it is easy to overlay an MS Word document with the CBS document is nothing short of a miracle, considering that no other kind of document can meet this standard.
Here is the nuts and bolts of the argument: a kerned document will not match the CBS document. A document produced by an IBM Executive will not match the CBS document. A document produced by an IBM Composer will not match the CBS document. Only a document produced with a default TrueType font will match the CBS document.
TrueType was not available before 1981. The spacing in TrueType is neither kerned nor straight proportional. It is something of a kludge, a computationally easy enhancement to proportional spacing.
Any document that matches TrueType spacing could not have been printed prior to 1981 or 1982.
Nope. The overall spacing will remain but on a per-character basis you can't tell anything. The "fr" ABC spacing is a perfect example. I can't tell if the "r" is underneath the "f" or not because the resolution of the fax is too low. The resolution of the fax is probably 1/3 that of a printer which means the C spacing on the "f" is not discernable.
I think these docs are fakes but these available faxes make it difficult to be definitive.