Are you sure you two are talking about the same thing?
My understanding of immutable infrastructure is the same as immutable data structures: once you create something, you don't mess with it. If you need a different something, you create a new one and destroy the old one.
That doesn't mean that the whole picture isn't changing all the time. Indeed, I think immutability makes systems overall more fluid, because it's easier to reason about changes. Mutability adds a lot of complexity, and when mutable things interact, the number of corner cases grows very quickly. In those circumstances, people can easily learn to fear change, which drastically reduces fluidity.
My understanding of immutable infrastructure is the same as immutable data structures: once you create something, you don't mess with it. If you need a different something, you create a new one and destroy the old one.
That doesn't mean that the whole picture isn't changing all the time. Indeed, I think immutability makes systems overall more fluid, because it's easier to reason about changes. Mutability adds a lot of complexity, and when mutable things interact, the number of corner cases grows very quickly. In those circumstances, people can easily learn to fear change, which drastically reduces fluidity.