Mengetu's story is promising, but is it a story or a "trailer" for his novel?

Some time ago I read Dinaw (?) Mengetsu's first novel, The Beautiful Things that Heaven Bears (?), and found it thoughtful and promising - a story about an African (Ethiopian?) immigrant in a gentrifying D.C. neighborhood - but also felt that it never quite got off the ground - once Mengetsu set the premise he kind of just let the story lie there - promising more than it could reasonably deliver (like the title). His story in the current New Yorker ("A good exit" ?) shows that he continues to develop his talents. There's a lot more going on in this story than in his entire novel. Mengetsu tells, seemingly autobiographically, of his father's flight from Ethiopia through the Sudan, where he worked in a port and was befriended by an older man, to Europe, imprisonment, political sanctuary, emigration to England, where he feels bitter and disillusioned and refuses to make good on his promise to the Sudanese man who helped him. This disillusionment not adequately explained, and Mengetsu rushes through the many events, but there's a richness of material here for him to work with - and, even more so, the story is narrated by a the African-American son teaching in a mostly white prep school in NYC, and that seems a promising issue to develop as well: the narrator explains how he feels displaced, alien, and how he tells this story to his students as a kind of healing, although in defiance of school practices. I talk about this as "promising" because, once again as I continue to see with New Yorker stories, this appears to be an excerpt or opening chapter from a forthcoming novel - not really a story at all but a trailer.