If you define sixualization as gender stereotyping in general, then yes, it's sixualization. But it's clear that men, as opposed to women, aren't portrayed as sixual objects. There is no eroticism in unnaturally muscled men, there's highly stereotyped power.
Women aren't portrayed as "objects", either. Physical attractiveness (in all its sometimes stereotypical and often subjective forms) is the common denominator of male fantasies, not the be all end all characteristic. The tough amazone is as much a male fantasy as the obedient school girl.
One keyword you used is "unnaturally" muscled, by the way. There is indeed eroticism in especially, but naturally muscular men. However, comparing males and females in this manner completely ignores that men and women put different emphasis on physical traits when discerning attractiveness - power or status, what you only see as a means for men to fulfil their own desires, is in fact cross-culturally the most imporant factor women look for in a man.
Point is there is intrasixual competition within both sixes, and women strife to be beautiful just as much as men want to be powerful. Which is why young girls are, sadly, so easily influenced and harmed by false and unattainable beauty standards. So I could see a viable argument against skimpy clothing from that angle.