I think it's important to remember that historical fiction doesn't have to be primarily about education, and it doesn't have to happen in a vacuum. It can be its own means of pure invention and can even be personal. In this case, for example, the author based the book on information she was given from parents and relatives and a story of her great-grandmother that she discovered later.
When I read Min Jin Lee's Pachinko, which begins in Japan-occupied Korea, it gave me a new perspective on the life of my grandmother, who lived in that time and place, not because it was an objective overview of events but because it was a diaspora invention that added to the overall pool of art and culture shared between certain pasts and presents. This book reminded me somewhat of that one, because it does much more (with language, with character, etc.) than just recount historical events.