One way of interpreting this simile is to say that as just as one technology has subsumed (become the focal point) another technology, so does a service mesh as a layer on top of a container orchestrator. A fifth layer as described in The Enterprise Path to Service Mesh Architectures --> https://layer5.io/books/the-enterprise-path-to-service-mesh

Not really, Kubernetes is a way to manage Docker containers. Istio just supercharges the network of a Kubernetes cluster. It doesn't really manage K8s clusters.