Pesachim 99b: Timing of Matzah, Kiddush and Haseivah

Rabbi Zweig analyzes the complex sugya on Pesachim 99b dealing with the proper timing for eating matzah and making Kiddush on Pesach (פסח) night. The Mishna states "lo yochal odom erev Pesach ad shetechshach" - one may not eat on erev Pesach until nightfall. Tosafos (תוספות) explains that this applies specifically to matzah due to a hekesh (textual comparison) between matzah, Pesach, and maror, since the Korban Pesach must be eaten at night. Tosafos raises a significant question: why can't one make Kiddush early on Pesach night, even if matzah must wait until nightfall? On regular Shabbos (שבת), one can accept Shabbos early and make Kiddush before nightfall. Tosafos brings a proof from the Gemara (גמרא) in Brachos about early Kiddush on Shabbos, suggesting that Pesach is different. Rabbi Zweig suggests that according to the Ramban (רמב"ן)'s view in Sefer HaMitzvos, Sipur Yetzias Mitzrayim (the obligation to tell the story of the Exodus) is intrinsically connected to Achilas HaPesach. If the din of Hagadah cannot begin until nighttime, and if the Four Cups are part of the Hagadah obligation, then Kiddush itself would require nighttime since it's the first of the Arba Kosos.