This isn't really accurate. It is true that ECDSA key generation is faster than RSA, but particularly in the context of SSH this doesn't matter. Also, I think you may be confusing ECDH and ECDSA. ECDSA (which is what the article is recommending) is the directly analogous to RSA in the sense that it provides eternal signatures. ECDH provides for generating individual session keys, but you can do that with classic Diffie Hellman as well, it is a completely separate issue from RSA vs EC.
Also, this line doesn't make any sense:
"Authenticity, not signatures, hence again DH + MACs, not RSA signatures."
You need an signature to have authenticity. The only alternative to this is pre-exchanging symmetric keys which isn't viable in the context of SSH.
You're correct, I'm not referring to SSH specifically, but speaking generally about the application of asymmetric crypto. The quote in GP, and GP's question, both seemed to indicate this broader context to me.
Also, this line doesn't make any sense: "Authenticity, not signatures, hence again DH + MACs, not RSA signatures."
You need an signature to have authenticity. The only alternative to this is pre-exchanging symmetric keys which isn't viable in the context of SSH.