The point is to tell the story of this game, which is clearly not just about Sophia, but about Sophia in her role as "A wife and mother". Therefore, it can be important to show decisive developments outside of sophia's direct involvement, if these could ultimately have a effect back on her. For example, if something happens between Dylan and Ellie, then that is something that can affect Sophia, because she is the mother of this two, I hope you understand that connection.
Anyway, I recently re-watched the movie "The Godfather" again. Probably one of the best movies of all time. And shall I tell you what I have noticed? No one would be so simple-minded as to conclude from the title alone that all scenes contain in this movie must have a direct participation of Michael Corleone. That would only have unnecessarily restricted the film.
BTW, L&P has already described in its game description that there can be events written from a different perspective other than Sophia in this game. Considering how popular the story about Dylan and Ellie is, I see no reason to cut back here. Rather, L&P should consider expanding these types of events.