> For example, Darwin first described the idea of natural selection in an essay written in 1844. [1] Talk about an important topic you could tell people something surprising about. If that's the test of a great essay, this was surely the best one written in 1844.

I think he's speaking broadly about what counts as an essay, and does have at least one example in there to illustrate his point. He's also an esteemed essay writer, and I think it's fair for him to talk about what he values in an essay without needing to justify any of it by saying "and also, this person that some people respect did it like that"