That's not my experience. My experience is that kubernetes does not introduce any noticeable performance degradation. My message was about nginx, not kubernetes.
Front TCP load balancer allows to use a single IP address for multiple backend servers. It allows for server maintenance without service interruptions. Or even server crash.
Ingress controller is nginx which does reverse proxying. It handles HTTPS termination and it handles routing to the application which is supposed to serve the request. It's either another nginx instance configured to serve static resources or some kind of HTTP server which implements an actual server logic.
I agree that having two nginxes for static resources seems weird, but that's not a big deal, because nginx does not consume much resources.