I don't really understand what you mean by this or how it relates to what I said.

I certainly wasn't suggesting that you can vertically scale a service to handle unlimited traffic on a single instance.

The point is that if you have stateless services, where the resources being consumed per request are mainly CPU and network bandwidth, then "scaling independently" is not a useful thing to do. You can just scale everything instead of artificially restricting which instances can handle which kinds of requests.