I don't understand 自己の視点から見た相手の発想に基づく表現 by itself either. Where did you see this expression? Anyway, based on the example sentences given, here is my take.
This phrase is probably to be parsed as:
The kind of expressions under discussion is not just "based on the interlocutor's prospective" but thought [by the speaker] to be based on the interlocutor's prospective.
Person A is getting married. They are now reporting it to someone else, B. A thinks, "If I say to B that I am getting married, they would probably say, 'Oh, wonderful. Aが結婚することになったのか.'"
In other words, A thinks ahead how B is likely to capture the event that A is about to report.
Always give as much context as you think unnecessary. How do you like your lamb leg steak? — Medium, right leg!