I think they mean "deterministic," not "immutable"
Yeah on further reflection maybe the "immutable" part of this is that I never use the Spotify UI to modify my playlist - it only gets changed during terraform apply phases, which may change the playlist in random ways on each re-apply.
For example - get AWS AMI where we can pin it or let it be latest.
> the spirit of immutable infrastructure
Immutable means changes recreate the resources. Not that that there won't be any changes. Mutable infra is where we keep patching the same resource and potentially end up in a state where we are not able to recreate it.