If nothing is declared unchangeable, then the organization will resist all change.
Organizational busy work tends to expand to fill the working day.
First law of Bad Management: If something isn't working, do more of it.
The fundamental response to change is not logical, but emotional.
The pathology of setting a deadline to the earliest articulable date essentially guarantees that the schedule will be missed.
The more you focus on control, the more likely you're working on a project that's striving to deliver something of relatively minor value.