Bad (and common) engineering managers avoid agreements on purpose to:

1) cover their asses

2) change anything at will

If you never agreed to anything, then you can keep demanding whatever, and blame whoever as well. It's a really shitty management style. I left such an organisation not too long ago where I would say that the engineering department survived not because of, but rather despite of the head of that department. First few years nobody had a clue what he was doing most of the days and when he decided to get actively involved it was obvious he had no clue about anything. He still has no clue but he's made sure to surround himself with incompetent yes-sayers to cement his position.

A real political genius.