In the absence of a control system that provides feedback to the progress to plan, the project is just wandering around looking for what Done looks like. The notion of emergent requirements is fine. The notion of emergent capabilities is not.
If we don't know what capabilities are needed to fulfill the business plan or fulfill the mission need, then we're on a Death March project. We don't know what value is being produced, when we will be done, or how much this will cost when we're done.
This is the role of the project control system. Without a control system there is no way to use feedback to steer the project toward success.