Apologies for not being explicit then: The combination of "Xthin" "Expedited Relay" and "Optimistic mining" that BU explicitly is pushing since you want to be pedantic about terminology, and he links the articles that describe it himself, so I'm rebutting not only what's in the article, but his own linked articles within it.
There is no "Optimistic mining" in Bitcoin Unlimited (not that I'd be against adding it as an optional feature).