Pesach - Mashiach: Bnei Ephraim Paves the Way

In this shiur, Rav Burg explains (based on a Torah from the Shvilei Pinchas) the secret of the Bnei Ephraim leaving Mitzrayim 30 years too early. What was their thought process? What was their mistake? Why does Hashem say that He will avenge their blood if they made a mistake?