I've read this passage and come to the same conclusion.

In fact, Judaism sees us as so ancient that according to one fifth-century interpretation of the Bible, the very first human being, Adam, was actually an androgynos. This explains why Genesis says, “And God created humankind in the divine image, creating it in the image of God,” referring to Adam, the first person, with a singular pronoun. But then, the very same verse says: “creating them male and female.” (1:27). “Them,” in this ancient interpretation, also refers to Adam: a single person who is both male and female. In other words, in this reading of the creation story, the first human being is described with a singular “they” pronoun to express the multiplicity of their gender.