“The idea that you can rely on looking for bad grammar or spelling in order to spot a phishing attack is no longer the case. We used to say that you could identify phishing attacks because the emails look a certain way. That no longer works.”
I was under the impression (will look later for corroboration) that poor grammar in phishing serves as a filter: phishers don't want to waste their time on people who won't get duped, so in an attempt to filter those people out early they send initial e-mails that will look suspicious to those people. If that's true, then the most obvious way to interpret the reason from that article doesn't apply. However, there might be some more involved reasons: e.g. if text generators make interaction with the potential victim cheaper, the reason for the filter's existence might disappear.
