> They initially told him the design was good as is and required no feedback and change, but once the project was about to be deployed they suddenly became very opinionated

Because the design usually is presented in a way that looks the most plausible, default-looking and approvable, hiding the real problems and decision points. And when the project is close to being deployed, the problems become visible.

Very rarely I see design being presented like 'here is the problem we need solve, here are the constraints, here are the unknowns, by this logic we come to this solution'. One of the reasons this rarely happens, is that in big organisations there is often a hidden agenda like 'I want as many people and departments as possible to start depending on me so I can get my promotion'.