We'll sum up Muller's answer in the video below because he wasn't definitive about it. He gave one of those "it depends" kinds of responses. But he hinted at what kind of sites should be using real author names.
His answer was based on Google's definition of websites that fall under the "Your Money or Your Life (YMYL)" category. It's not as threatening as it sounds, but Google takes this type of content seriously.
So here are some quick examples of YMYL types of sites that cover topics such as financial and medical advice, health and safety, shopping, civics, government and law, etc. Pretty much anything that can negatively impact someone's life financially or their health, happiness, and safety.
Muller said that YMYL sites should generally avoid using generic author names, and here's why. He mentioned Google's E-A-T concept, which stands for expertise, authoritativeness, and trustworthiness. This means that YMYL sites that give financial or medical advice should have verifiable and trustworthy content written by an authority figure and expert on the topic.
For non-YMYL sites, like "theater news, for example, or SEO news or anything kind of random on the web," it's not as big of an issue regarding the author's name and trustworthiness. That's where Mueller said it was "less critical how you frame this."
But here's another curveball Muller threw at us. He believes that an author's name plays a role in creating some types of structured data. This is where you'd want to use a real author's name to be featured as rich results at the top of a search results page.
Muller ended and said, "...I think a generic news and reviews and tickets website, you wouldn't necessarily worry about the name of the author that you specify there." So long story short, non-YMYL sites shouldn't have to worry too much about who wrote it and can get away with using "admin" or "author" or no name at all on articles.
On the other hand, YMYL sites should prove their credibility by using real names on articles and possibly have author bios to further prove their expertise, authoritativeness and trustworthiness on the topic.