Adaptability as a principle

So, how come there’s a principle about adaptability when the PMBOK Guide is supposed to be compatible with and recognize both approaches?

The reason is that we have two subjects:

• Adaptability for the product we build in the project
• Adaptability for the project management system

You can build the product using an adaptive or a predictive approach depending on the type of product. However, for the project management system itself, since it’s about complex relations among human beings, you need to have an adaptive system. It means that it’s best to have a base system, and gradually enrich it during the project; or if that’s not possible, at least revise the system to suit the environment as you progress.