I am unfamiliar with Islamic practices so I won't comment about the traditions that spur this development in Saudi society. However, it demonstrates the importance and struggle of fundamentals that underlie any city. With this marked example of providing facility to women to mitigate the strict rites and regimens of their culture, a unique step in urban planning is created that would probably not be witnessed in any other place.
At least in fiction, the notion of a womens-only environment isn't completely new. The ecofeminist novel The Gate to Women's Country by Sheri S. Tepper explores society where genders are purposefully segregated in a post-apocalyptic setting. The idea is drastic - at least for Western and other egalitarian cultures.
In a way, it is great to see such a strong will in urban planning come into play. Usually the hallmark of utopian thinking (ironically most which did not succeed due to the unrealistic idealism), has planning practice been dulled by a please-all, compromise approach? Although the gender separation probably wouldn't work in other cultures, Saudi's setting and resources could see something that works and may even change the culture in which this development sits.