Old mailing list posting that I can't find right now (I was looking for something else when I came across it).
I think it makes some sense, too - by what we know, boys can wait for a couple of years for adulthood initiation if they have to, no biggie, but a girl reaching menarche has to have an adulthood initiation right now, because that's not the kind of thing you can leave hanging around for a while. On the other hand, I could very easily see the adulthood then veer off in some different direction for would-be Vingans.