If other cues, would "wiry black hair" sufficiently tip the balance to make you envision someone of similar appearance to sub-Saharan African peoples in this world?
If neither of these would be enough, what could a writer do without comparing her character's skin to food to indicate that general appearance sufficiently for you? Note that the character in question has skin that's dark brown but not so dark that "black" would be an accurate term in a fantasy setting where that term wouldn't come with the cultural baggage it has here -- we only call some fairly pale brown people "black" because of cultural baggage, not because of any proximity to the actual color black! If I tell you someone in a fantasy novel is black-skinned, I want you to see black skin, like Cherryh's atevi.
I ask because it took me most of a Rex Stout novel to realize that the "dark-skinned" young woman character was not, in fact, meant to be African-American, so I suspect that different people are (or at least were!) reading different things into the same words.