"Expert Review" here being a thing their program does, not the concept of having experts review something. I didn't know this and was quite confused by the headline. A brief explanation of what it is from one of AV Club's linked articles:
"Last summer, Grammarly launched eight specialized AI agents to “provide targeted assistance for specific writing challenges.” The idea has since evolved to hoover up famous authors’ work. Earlier this week, Wired reported that using Grammarly’s “Expert Review” allows an approximation of Stephen King and Neil deGrasse Tyson to nitpick your work. While Tyson has the opportunity to say whether he’d like to be turned into a chatbot, other authors, like Carl Sagan, cannot because they are dead."