Many signatures were of known illiterates, many more of small children. Page after page was written by the same hand. Authentic signatures were often obtained by threat.
So there was a study of all the illiterates of the time to see if they signed. I have no doubt there were some shonky signatures, but tens of thousands of them?
We don't know we weren't there, but Ned was most assuredly a hero to many, and that is what the question begs.