Applying a patch is "make these changes to your existing state".
That dependency on existing state is a difference, and it seems to map reasonably well to what declarative/imperative seem to usually be used to mean in this context.
2. "make these changes to your existing state" is still declarative
It isn’t though. It’s “please make the state look like this eventually”. You do not patch state, just spec. Controllers effect the changes.
That said, the parent is wrong that a full manifest is declaring the (etcd) state in a way that a (strategic merge) patch isn't--both are declaring etcd state, but a strategic merge patch is doing so in finer-grained increments. A strategic merge patch can declare zero state or many full manifests, while applying full manifests can only work in increments of complete resource manifests. But both are telling Kubernetes "this is your (etcd) state now".
[0] https://kubernetes.io/docs/tasks/manage-kubernetes-objects/i...