There are things besides fitness that are relevant to combat situations. In the movie Whiskey Tango Foxtrot, which takes place in a war zone in Afghanistan, we see the female news reporter is able to talk to the female residents in a combat zone and gain information about who was sabotaging a US-built well. The male soldiers weren't allowed to speak to the women of the village, and had no way of getting this info.
Women make up 50% of the world population and sometimes you just need a female soldier to properly work with the locals. If men cannot get information from some populations because of their gender, then it makes sense that rules might be slightly bent to allow women to take part in combat roles. As a soldier, I wouldn't want to be miss relevant info just because no one in my troop could talk to half the local population- that ignorance of knowledge puts my life at risk too.
On the tv airing of "How to Lose Your Guy in 10 Days," they have a scene where they are playing a bluffing card game call "Bullshit" where you can call bullshit on people who you think are bluffing. They replaced the word "shit" with "spit" so everyone is shouting "bull spit" at each other. I found this to be so ridiculously lame that it made it kind of funny.