Wow it's been awhile since I last visited this thread! I agree with @CherryBunny, the husband was not changed at last minute - it was just a rumour that's not proven true and based on people's assumption because of the spoiler. Like what I've written above, I truly believe that Taek was planned to be the husband since the start. It was fitting that they had JH narrating the story to throw us off at the beginning....but then his narrating was telling his own story and mistakes when it comes to love. He hesitated too much and that was the message that the writer wanted to deliver to the audience.