Girls as boys?

http://www.nytimes.com/2010/09/21/world/asia/21gender.html?_r=1&ref=families_and_family_life    

     I was sitting outside one day when i stumbled upon a New York Times newspaper. I skimmed it for anything interesting to read and found a very good article about girls being disguised as boys in Afghanistan. There is a great pressure among families in Afghani culture to produce boys because it is beneficial in both economic and social ways. However, sometimes when a family can't, they do the next best thing, turn one of their girls into a boy. I thought, this must be causing a big controversy, these families must have to hide the girls true identity as a secret. What I found upon reading however, was much the opposite. People are very aware that this happens, in fact they have a special term for these girls, bacha posh.
     In a society where women and girls cannot go anywhere alone a bacha posh can escort her sisters to the market. So in a society where women are seen as a weaker sex, dressing them up as boys solves the problem? Does this not prove the fallacy behind the thought process? If men and women are truly and fundamentally different, then putting boy clothes on a girl should not enable her to do all the things that boys do. But in Afghanistan, that is exactly what it does. People know that these girls are impostors, that they are not truly boys yet they let them have freedoms traditionally reserved only for men simply because they look like boys. If looking like the opposite sex is all it takes to attain their status in society, does that not show a fundamental flaw and element of hypocrisy in said society? Does this not show that girls are equally as capable as boys given the proper social structure? Does this not prove that society, not biology or the way "God created us" determines gender differences?