One thing I disagree with is that it's "the best optical illusion of the century." They've happened upon an androgynous facial structure and picked two 'looks' that represent typical ethnic features. The 'girl' looks like any fair skinned, brown eyed and haired mid 20's girl. The 'guy' looks like either tan skinned, brown eyes and hair or of Mexican or South American origin. Most of the guys I know that are tan have brown hair and eyes - many of the fair skinned girls that I know have brown eyes and hair. All they've done is create images of 2 archetypes that many people would assume as male and female.
Now after thinking about it, the face is not androgynous. If it were truly androgynous then it would appear to be neither male nor female. If you perceive either more than the other, then it's not true androgyny.