Well... I think you are partially right. If the people signing the documents had a good faith belief that they were authorized to sign it, they would have a valid defense to a forgery charge. That could be why we have not seen anyone charged in this debacle.

But, this case is a bit unusual.  To my knowledge, there was no real "Linda Green" with the authority to sign, or to authorize others to sign her name.  I think they just picked that name because it was short and easy to spell. The people in charge, who instructed people to sign "Linda Green" on documents should be investigated.

The required intent for forgery is only the intent to fool people into believing that something false was genuine.  This is supposed to safeguard the confidence in the genuineness of documents relied upon in commercial and business activities. 

Aside from the forged signatures, the important question is were any of these documents false?