One would never know if an Airlines FCOM was "Boeing" or "non Boeing" unless you have access to the original Boeing documents for your fleet specification. Almost all airlines customise their FCOM's to how the current Chief Pilot thinks it should be done.
Our entire Boeing Fleet from B737 to B747 (5 different types) the FO starts the engines so the Captain can manage the operation, however we are by no means "Boeing 100%". How far each type is away from "Boeing" I am not aware of but that is how my airline operates.