Anything can be part of an identity. “Blogger” could be part of my identity if I so chose. It still indicates something that I do. If I stop blogging, I cease to be a blogger, no matter what my self-conception is. To the extent Dan indicated otherwise (though I don’t necessarily think he did), I disagree. Yes, some people’s only route to happiness is through polyamory. They still have to choose to do it.
Some people can only be happy if they are acting in plays and movies. Those people do not have a career or lifestyle orientation. They have a thing that they need to do. We don’t use the word “orientation” to describe something that someone needs to be happy. We use the word “need” for that. In a sex & relationship context, the only thing that people use the word “orientation” for is to indicate a sexual orientation. People who call polyamory a “relationship orientation” or some other half-term are only doing so to attempt to draw parallels between polyamory and a sexual orientation, which I think is bullshit.
If you want to say that you were born poly, and you can’t be happy unless you’re poly, just say that. Don’t try to draw a false equivalence between your relationship style and other people’s sexual orientation. It’s not the same thing.