Apparently it’s not. From the link (which I’m not to afraid to click, I guess):

Google is rolling out one of the most significant changes in Gmail’s history: users can now change their primary @gmail.com address without creating an entirely new Google account. The feature, unavailable for over 20 years, is being introduced gradually.

Of course, I’d also like to see that from a more reputable source as well, or from the horse’s mouth.