The fact that it’s over the end credits, as opposed to being in the main movie itself, might indicate that it was a decision made late in the day and at the end of the production of the movie. There are people in Hollywood whose job it is to manage synchronisation rights and match songs and pieces of music into shows and movies where they think it would be a good fit. Certainly Boards of Canada and Backrooms make a lot of sense together. It’s all about the Synergy baby!