It's sex not gender. Looking at the text it is only the more androgynous elves that seem blessed with this ability, their gender doesn't change only their sex does.
Personally I'll be fine with them in my game.
You can read the rules for Blessing that way, where the special androgyne retains the *central gender*, despite switching physical sex organs.
However, Corellon is a shapechanger, who oneself takes on any form, including any gender and any sex (and any orientation). Androgynes are the sacred because their being in the middle of the sex-gender spectrum, are *suggestive* of symbolizing the entire spectrum. They are a vision of the entirety of everyone, holistically. But those rare shapechangers among the Blessed, actually go beyond the potential into the actual, and are shapechanging dramatically into any location on that spectrum.
I prefer to read the rules as saying, when certain of these androgynes can change ‘sex’, it means they can switch from extreme male physical features (heavy testosterone) to extreme female physical features (heavy estrogen) − especially with regard to secondary sexual characteristics − and fluidly transition the entire spectrum.
This understanding of being anywhere on the spectrum helps reallife players who seek to *appear* as a trans man or a trans woman, especially with regard to secondary sexual characteristics.
A more dramatic transformation makes the storytelling more interesting. If it was nothing more than what is happening in someones clothes, few people would ever even know.
The sacred status of androgynes has reallife examples in various cultures. It is an interesting phenomenon, and worthwhile to include in any setting. (Even in settings that lack Corellon or polytheism generally.)