Growth is always non linear.
... the incidence of test failures is directly proportional to the square of the size of the crowd multiplied by the rank of the senior observing official [Augustine's Laws]
The dynamic behind this law is simple: A large crowd of high dignitaries means that the event is planned according to external, not internal, events.
It is easy to look at this diagram and believe that you're seeing a defined process. You're not. What you're seeing is an optical illusion.
"model" is just another name for a guide to anticipating the future.
Cultural changes have a much greater potential impact than process changes because one cultural change - such as driving fear out of the workplace - can affect hundreds of process changes.
Feedback works on continuity. The pieces in the model cannot be too large (or response will be slow), and they must be stable (or response will not be predictable).
Error prone modules are born error prone and stay error prone.