(a) Then how did Tom Hanks get involved? “Starring actor” was included in the premise.
(b) If he knows he’s the last black man on earth, sure. But that would suggest a predictable, but unavoidable tragedy, known months in advance to give enough time to actually produce the movie.
Have you considered that
(a) documentaries do not need actors, and
(b) if they did, the last black man earth could star as himself?
(a) Then how did Tom Hanks get involved? “Starring actor” was included in the premise.
(b) If he knows he’s the last black man on earth, sure. But that would suggest a predictable, but unavoidable tragedy, known months in advance to give enough time to actually produce the movie.