tldr: articles and interviews are proofread and corrected by english native speakers.
was?
In the interest of full disclosure, I am myself a migrant in an English-speaking country (a Greek living in the UK). I know first hand that there is a big difference between having been taught English as a foreign language, and actually using it to speak with native English speakers day-in and day-out.
My first years over here I had real trouble talking to people and making myself understood, or understanding them, although at the same time I was perfectly fine reading English literature and textbooks, participating in lectures and writing university assignments. I believe many foreign students (if not all of them) had the same issue.
There's an assumption that the way you speak a language reflects your general intellectual skills, but when it comes to non-native speakers it's just wrong. People taught a language as a foreign language acquire oral and written literacy skills in a different order and pace than native speakers. For instance- two friends of mine can read and write Japanese, but can't speak or understand it when spoken.
Basically, speech can be much harder than text for foreign speakers. So using the disparity between oral and written skills was already a very shaky piece of "evidence" in the original claim- even before reading Naomi Wu's explanation. It reminded me of classic conspiracy theorists looking at the shadows in pictures of the moon landings.
I think it comes down to reading a lot and absorbing that formalism, but not really speaking that way because, well, spoken English is a different bird.
(er, not trying to make some political comment on gender roles etc, just genuinely interested to hear from a speaker. I guess I can just google it :)
On a side note, it is a pain in the butt to search for Dakota as opposed to Lakota on Google because it keeps giving Lakota pages. What a pain.
Like I say above, I had a big problem with that in my first couple of years in the UK. I once spent an hour having a conversation with a man from Glasgow. To this day, I have no idea what he was talking about. I didn't understand a word he was saying, so I just nodded along politely. I might have been agreeing to the need for the extermination of all sentient life or that the Earth is flat, for all I know.
I got better at it. I can now understand about 40% of what someone's saying in a Glaswegian accent. I love Scottish accents btw- probably more because I don't understand everything being said.