you're lyng your ass of here... none of the shit you just said is in the story... in fact in the first chapters of the manga version we can see plenty of exemple of them not being sluts: reina eavesdrop on some classmates calling her a slut and that she probably fucks with other models...
nothing about that is known until now... in the first chaptar of the hentai we could say that was the case but with the other chapters of the hentai making them all cute instead of just horny sluts and now this manga showing them just as basket ball players in other school before meating...