I find this line in the article most interesting, "This preference is because Gmail is a very popular service that people associate with legitimacy and trustworthiness."
My question upon seeing that is, "Why would you use the service, particularly a free service where people can create "burner addresses," to be legitimate or trustworthy?"
If you're receiving any email message from an unfamiliar sender and are not expecting it, the one and only piece of advice is: delete it and move along.
The fact that Gmail as a service is rock solid is a completely separate issue from it's users being either legitimate or trustworthy. You judge how legit and trustworthy something is not only, or even primarily, by the email service used to send it.
This is why I'm pretty much adamant that there is no technological solution to these issues that will ever come close to being really effective. It's only user education that allows anyone or any entity to stand a chance. And, to me, what's sad is that education really should not be necessary for most of these phishing expeditions at this point. If you don't know the sender, and aren't expecting the message . . . How many years and how many scams must occur, and be widely publicized, before this becomes a "baked in" behavior? I just don't know and there is definitely an element of, "You can't fix stupid!," involved, too.