I don't think it is. Usually, such titles suggest fictional or semi-fictional content rather than being based on real events. There might be elements inspired by real life, but it's not a pure true story.
It could imply that there is a story, perhaps a narrative, that is very 'black' (which might refer to aspects related to black culture, experiences, etc.) and is based on real - life events.
Well, 'black af' might be an expression. 'af' could stand for 'as fuck' in a very informal way. If it's based on a true story, it means that whatever this 'black af' thing is, like a movie, a book or a show, it has its roots in real - life events.
One example could be a documentary about the civil rights movement in the United States. The events and the people involved were real, and it could be considered 'black af' in the sense that it powerfully showcases the black experience during that time of struggle for equality.
One example could be a documentary about the civil rights movement in the United States. It would be deeply related to black experiences and based on real historical events, which is very 'black af' in terms of its focus on the black struggle for equality.