The point was that Go's http stack and standard library and runtime being written all in Go gives me confidence that any Go code I write on top will enjoy the same performance characteristics and that there will be very few surprises. It's predictable due to its uniformity.
So CPYTHON can not in fact deliver those performances. But CPYTHON can be extended through Japronto to achieve them. I'd say it's still misleading, since casually when we refer to Python, it means CPYTHON.
Go's primary implementation provides all the fast goodies needed for fast performance. There could be a slow Go compiler which didn't, but when you say Go, it refers to Google's implementation.
You could argue that at least, CPYTHON makes it easy to extend the language with C. So Python language extensions are trivial to use compared to some other languages. So at least I'll give you that.