It's designed to be more CPU-efficient than NodeJS or Python, but if all your heavy lifting is really in Postgres and other services you're calling, it doesn't matter and it's a bit pedantic. I think Golang was designed for something in the middle, maybe building a DBMS or some deeper backend.
I strongly disagree with this statement, Golang is excellent for building backends and just the orchestration of all the services you are calling is better done in a typed/compiled language with great multi threading support and fast compilation times that is exactly what Golang excels at.
This is trying to solve a problem a lot of people never really had. I've never been working on an Express backend and thought gee, wish I had threading.
using a systems language for a backend mainly gains throughput over python than latency. each request might not be faster but you can handle 100x more users.