https://en.wikipedia.org/wiki/Express_Data_Path is a feature of recent Linux kernels allowing you to bypass/replace most of the normal Linux networking code, allowing for higher performance. Some network cards will even run your network code directly on their hardware.

(not sure what GP meant, just providing the reference)

I think they were confused by the term “netcode”, which in game developer parlance means “code which implements networked gameplay in a multiplayer game”, rather than “code that implements networking in an OS”.

Yeah, our netcode forward predicts from the server state to the local time to allow the local player to see their own character without network artifacts, and see other players in approximately their true location. It's the 'server authoritative, with client side prediction and rollback' technique. Consult Gaffer On Games' blog posts to learn more.