I can't say that I agree with a lot of the article.
I'm a binary trans woman. The only of that that tells you my gender identity is "woman". I'm binary and I'm trans, but neither of those are gender identities, they are simply ways of telling people more about my gender identity.
Additionally, I'd argue that gender identity isn't comparable to a style or sexual preference There are gender non conforming, asexual binary folk, and there are allosexual, gender conforming binary folk. All of those folk are binary, but there is no overlap in sexual preference or style.
And in the same way, for many folk, non binary isn't a gender identity either. It's a label that tells you what their gender identity isn't, but that doesn't automatically tell you what it is.
But ultimately, I think we're in agreement on the overall point. Nonbinary is a starting point to understanding someones identity, not the end. There is an infinite world of possibility that all gets wrapped up in to that term!