The same This American Life episode raised serious doubts about Dr. Steel's claims, which is mentioned in the article you link:

> When reporters tried to corroborate Dr. Steel’s claims, however, holes started appearing, according to the This American Life episode. Chief among them: There actually was a real Dr. Robert Ho Man Kwok, and his biographical details seemed to match those provided in the letter, like his professional title, the name of his research institute, and the date of his move to the US.

> While both Dr. Steel and Dr. Ho Man Kwok had died by the time the digging began in earnest, their surviving family members were able to shed some light on the situation. Dr. Ho Man Kwok’s children and former colleagues were adamant that Dr. Ho Man Kwok had in fact written the letter. Meanwhile, Dr. Steel’s daughter said her father was a lifelong prankster who loved pulling one over on people. With this testimony in mind, the reporters came to the conclusion that Dr. Ho Man Kwok was most likely the true author and Dr. Steel had taken credit for years as an elaborate practical joke.