The first one gets chosen for metaphorical and thematic significance. Even from the character's point of view, though he may delude himself about motives. If it happens to alert the characters about correct actions later, there's a touch of irony about it, and probably it needs to be either given a twist, or have character comment on how this isn't a fairy tale.
The second one is just history. A character might comment on the coincidence of having to go hunt for his wife over sea and land like in the tale, but it's the sort of thing that happens.
Not that it can't be retold by a character for reasons of metaphorical and thematic significance. . . says the writer, having just written a scene in which a son and mother discuss the reasons why she can't rescue her husband, should he fall captive, the way her grandmother rescued her grandfather -- and the son thinks but does not say that, in addition, his mother doesn't love his father enough to do that.
