It's not exactly about the folder, the IaC from a single folder / project can be instantiated in multiple places. Each time you do that, it has a unique state file, so I usually hear it referred to as a "state". In cfn you can similarly deploy the same thing lots of times and each instantiation is called a "stack", so stack/state tend to get used inter-changeably.
And yes, that's a succinct rephrasing.
When you first use iac it maybe seems logical to put your db and app server in the same "thing" (stack or state file) but now that thing is "pet like" and you have to take care of it forever. You can't safely have a "destroy" action in your pipeline as a last resort.
If you put the stateful stuff in a separate stack you can freely modify the things in the stateless one with much less worry.
And yes, that's a succinct rephrasing.
When you first use iac it maybe seems logical to put your db and app server in the same "thing" (stack or state file) but now that thing is "pet like" and you have to take care of it forever. You can't safely have a "destroy" action in your pipeline as a last resort.
If you put the stateful stuff in a separate stack you can freely modify the things in the stateless one with much less worry.