I don’t really see it. Even discounting the glossy accomplishments, Armstrong fought and beat more great fighters than Charles did. Quite clearly. Charles’ quantity of great wins is based primarily on fighting the same guys over and over. Armstrong faced and beat a broader stream.
I get into arguments with my buddies about this all the time, my personal Mount Rushmore is Robinson Greb Armstrong and Pep, my buddies generally agree with me on the first 3 but pep is where we disagree, some say Bennie Leonard, some say Joe Gans, some say Sam Langford, ect, in general if you have any combination of these men in your MT Rushmore, it’s hard to disagree with