But they didn't say "rock stars" they said "women in ROCK". that means they are a part of rock.
and you know damn well that an issue of "men in ROCK" would actually have men in rock. They couldn't get away with saying that Justin Timberlake was a "man in rock".
If they felt it necessary to mention pop stars, they could just include interviews with them inside the issue.
but it is an insult to present a "women in ROCK" issue and for the cover, to not include women that rock.