The statement was that all the works except two were unequivocally first century. In fact, four are almost certainly second century, and parts of the rest are debated. More than four is a whole lot different than two.
Not really, when you are talking about four letters. One letter is the equivalent of one chapeter of a Gospel. A Gross exaggeration might have been to say that none of the NT was written after AD 100. Virtually all of it was written before.