The difference betwen deploying an instance of a stored environment and generating that environment from some prior state is the generative process, which can f

The difference betwen deploying an instance of a stored environment and generating that environment from some prior state is the generative process, which can fail or change in unexpected ways due to network conditions and other factors. CSIEs are still a generative process. The difference with what you call PCFT is that the generative process isn't swept under the rug and codified into a versioned image unless it's really necessary for performance reasons. The result is that it's easy to maintain a clear distinction between machine state and human instructions. For a trivial example: a list of packages that humans decided are necessary for the system versus the final output of 'dpkg -l' after all dependencies have been resolved. With chef/puppet/etc. the code used to generate instances represents a human-created description of what the environment is supposed to look like, with as much version-control and referenced documentation as is necessary. With a versioned-image approach, all you have is the one-dimensional history of the image in question.