Actually, it appears that demi-sexuals themselves identify as being on the asexual spectrum. From the Demisexuality Resource Center:
http://demisexuality.org/articles/what-is-demisexuality/
Grey is between sexual and asexual on the spectrum per various resources so while not asexuality, it is on that spectrum as well. It's rather like the spectrum between gay and straight. There isn't a gay-straight dichotomy, but a spectrum that runs from "always homosexual" through degrees of bisexual to "always heterosexual". Grey is basically in the space on the sexual-asexual spectrum that bisexual occupies on the gay-straight spectrum.
This seems like a bit of a pointless debate that you and
@BetteTheRed are having. The bottom line is that there is a non-zero percentage of the population of various descriptions who can live without nookie. Some identify as a- or demi- sexual, some do not. I know a couple of them on another forum.
And this all began with arguing about Jae's contention that gay people can live without sex, which is only true for gay people who are also towards the asexual end of the asexuality spectrum. Many, if not most, gay people are not in that position; they want/need, and are entitled to, a sex life and the existence of asexuality can't be used to justify denying it to them.