The advantage for the film makers of this film compared with others like Tirpitz, Bismarck, Graf Spee is the back story. The front story, OP Dynamo, is the framework but the little boat owners have a wider range of stories from which to draw and of the retreat, even more.
The new Dambuster film, if ever, is in a rigid setting where as the Dunkirk back story could be completely different from the earlier film.