The results of this test don't really prove or disprove Naipaul's claim. He never said that any differences in the writing of male and female authors are blatant, and if subtle nuances of gender are present in writing, the inability of the reading public to decipher them doesn't disprove their existence. Furthermore, small samples like the passages in this test obviously make it more difficult to distinguish gender, considering the proposition that male and female authors are different on some fundamental level does not mean that the language they use is necessarily dissimilar, but that they perceive the world around them in different ways, and therefore write about their perceptions in different ways. A couple of sentences is certainly not enough to get an accurate sense of an author's writing.