Once the microprocessor is designed, there is typically a large amount of room for that design to be made more efficient through optimization. The control unit specifically can be subject to logical minimizations.
As the specific requirements of each component are understood better, through simulation and prototyping, the clock speed of the system can be increased to reduce waste.
The most common operations, memory loads, memory stores, and basic arithmetic can be laid out in such a way that they can be performed quickly and easily.
The word "optimization" is likely a misnomer because it is unlikely that the best possible solution will ever be found to the complex problems that arise during microcontroller or microprocessor design. However, there are typically ways to make things better, even if they can't be made optimal.