From TFA:
I tested nginx as a proxy, serving static files, and serving nginx-generated redirects. I tried changing all the relevant ssl parameters I could find. All setups resulted in the same SSL performance from nginx. I even tried the setup on more than one server (the other server was quad-core nginx got up to 75 requests per second).
So "all the relevant ssl parameters I could find", no details about what those involve, and the surprising result that it made no difference.
In the same situation, I might think I was doing something wrong...
And then this overarching statement:
Never let nginx listen for SSL connections itself.