Maybe I'm naive, but I think it's possible that Albie realizes that the Peter Principle is a real thing, he's an excellent recruiter, just doesn't have the right skill set to be a HC. He loves BU, so whether he decided, or BU decided, I think this may not be a "why would Albie agree to that?" scenario. Maybe he is fine being an assistant, and perhaps even at BU if Jay really does become HC and wants to keep him on.
FWIW, a parent of player said to me at the Beanpot in Albie's first season: "He has no f-in clue what he is doing, no clue. It's a complete joke". Not knowing that parent prior to that exchange, I didn't want to put too much stock in one statement, thinking it could just be frustration over playing time. But I have sort of wondered if a change might come quicker than we all thought going into that first season.
Anyway, I think it's a great move either way for BU.