Perhaps the paragraph is coming to teach us something about the nature of the מצוה of סיפור. Perhaps you might have thought the obligation is to simply recite over the story that occurred in Egypt. It is a set of facts to report. This would be limited. It would seemingly add nothing to those who know “all the Torah”. However, perhaps the obligation is not to simply recite a story, but to be involved in discussing the area of Yitzias Mizraim. This discussion can start with the basics, but will spring board into an array of topics (Hashgacha, prophecy, creation, idolatry, free choice, etc.). It is an involvement in an area of study. It requires questioning and analysis that enters you into infinite area of study.
See רמבן on אנכי ה for elaboration of fundamental principles the event of the exodus establishes for us.