I understand why you wrote the article this way, I think the lesson here is “we have learned why Japanese textbooks do not teach the content in this order” and there are a couple reasons why this order is not good:

1. It relies on people not understanding certain things. In general, you cannot expect people to have exactly the right misunderstanding necessary for a lesson.

2. Spending extra time with Hepburn reinforces it, and it shouldn’t be reinforced.

I am in general extremely skeptical of lessons which try to engineer a way for the students to make mistakes. What I have seen in real classrooms and in informal teaching is that the mistakes are habit-forming and the outcomes of this kind of engineering are unpredictable.

Mistakes are appealing to the developers on HN because we understand things more by seeing them fail. But this does not mean that you can engineer somebody to experience the same moment of enlightenment that you did, because it requires constructing the same (incorrect) mental model that you had when you made that mistake that led to useful insight, and it both difficult and counterproductive to try and make that happen to students. Give people the best chances to learn by giving them the best chances to avoid mistakes, and the mistakes and insight will happen organically on their own, in unique ways for each student.