Really, circamore, you’ve well established in more than one forum that you can make up in your own head wonderful explanations for all sorts of shoddily constructed manga.
But this business about how you get stories precisely how the authors intend for the original audiences to get them while others must labor mightily to see the deep cultural reasons why (for example) a writer sets up and develops a series of conflicts then declines to resolve them except by handwaving them away is really a bit rich—literary interpretation and fanfic/headcanon are distinct activities.
I have to doubt your good faith when on the one hand you give us extended lectures on how one part the story must be understood in deeply specific cultural terms about just how traditional and conservative the very specific social setting is, then handwave away a gaudy Western-style wedding between lesbian stepsisters, ffs, that would be utterly alien to that social class we’re supposed to understand so deeply.
Your arguments here amount to a game of interpretive three-card monte, with “cultural context,” “authorial intention,” and “intended audience” brought in to explain away obvious problems with plot construction and charaterization.