It should have been dwarves. It would have explained the classic trope of "Where are the dwarf women at?"
Funny you should mention that...
IMC, I won't be using this Blessing of Corellon as written, partly because Corellon just doesn't exist, but also because my elves aren't like that and do have fairly fixed gender roles (and, incidentally, have a matriarchal culture).
However, there are various gender-fluid races of one sort or another - Changelings can change sex and/or gender (along with most other things) pretty much at-will, Dragonborn can change over the course of months. And dwarves have no fixed sex until they reach adulthood, at which point they adopt one for the rest of their lives.
In addition, I will be adapting the Blessing as something granted by the gods, either allowing a one-time switch for some characters or allowing some others the ability to switch overnight. That last will be something that's available to characters of any race (actually, including elves, despite what I said above).
(It's possibly also worth noting that, again IMC, Warforged don't have either sex or any concept of gender - as a constructed race, such things just don't apply to them. So it is possible in my campaigns to play characters of any sex or gender, or indeed none - at least, when we're playing in Eberron.)