The anon has misstated the meaning of forgery. A forgery is a work that is made to look as if it has been produced by a specific party, when it actually has not been. From the Merriam-Webster dictionary:

the crime of falsely and fraudulently making or altering a document (such as a check)

It does not mean an "unauthorized copy". In this case, claiming it is a forgery would make sense as a work of fiction is intended to be understood as not real, while this document was made to look like a series of factual reports of actual happenings, i.e. the intention was to look real when it in fact was not. If someone created a fake FoIA document and circulated that as if it was real, it too would be a forgery (the false production of a legal document) and not a "work of fiction" because the intent would be for people to consider it to be real.