I really do feel polyamory is a part of my sexual identity. Since I can remember, I have always been drawn to romantically love more than one person, which is what caused all sorts of confusion and anguish to me before I realized I wasn't just a serial monogamist. That is a part of me I don't feel will ever change, so personally I do feel "hard wired" to non-monogamy.
The only way choice factors into this, again in my own observation, is how I choose to develop and explore relationships with people. I don't at all think relating polyamory as an aspect of my sexual identity is counterproductive.
I think what is counterproductive is to pidgeonhole sexual identity into just gender attraction in a purely monogamous way. I wonder how many marriages and relationships could be saved if people were more honest and open-minded to exploring their sexual identities in a way that might exist outside of the framing of monogamy.