There's a quote in the article that, I think, also accurately summarizes it:
To people like Haigh, the computer historian, this is a case of simply defining “e-mail” in such a way that nothing else fits.
“He is trying to make a definition of e-mail which would exclude everything before his system,” said Haigh in an interview. “That’s not how you get to do it. The person who says they invented an airplane in 1918 doesn’t get to say, ‘It’s only an airplane if it has six windows, it’s built with metal, and it has a retracting undercarriage.’”
This guy got a copyright on a computer program he named EMAIL, and he's milking the story for everything it's got. Hardly surprising, if that is one's one claim to fame.