You are both slightly off. It's entirely up to the parties bargaining how much discretion the employer has to adjust terms during the life of a collective barg

You are both slightly off. It's entirely up to the parties bargaining how much discretion the employer has to adjust terms during the life of a collective bargaining agreement. For pay specifically, it's not uncommon for the union to propose wage floors and allow some individualized bargaining. It's also not uncommon to specify a full wage schedule for the sake of transparency. The workers get to decide what makes sense for them. Sometimes they decide on different systems for different career tracks.