“Girls are particularly cautioned”

17 Again
A reader alerted us to this message at the bottom of the New York Times review of 17 Again, the new, sure-to-be Oscar-winning movie starring Zac Efron:

“17 Again” is rated PG-13 (Parents strongly cautioned). Girls are particularly cautioned.

After a quick plot synopsis (a dude’s life was ruined because he turned down a basketball scholarship after his girlfriend got pregnant), reviewer Manohla Dargis notes “the story’s obnoxious implications” are that “sex, meaning girls, can ruin your life.” She makes clear that the movie’s female characters are (surprise!) little more than simple stereotypes. So presumably this is what the “special girl warning” is referring to.
But if that is the case, doesn’t sexist content merit a warning for boys AND girls? The assumption that a negative portrayal of women will only affect girls is simply crazy. Young people of all genders are deeply affected by repeated sexist portrayals of women in movies, music, and culture more generally. Yes, it can have very different effects on boys and girls. But how is it worse for a girl to think of herself as having to choose between harpy or sex object than it is for a boy to view all women as harpies or sex objects?
And what if the warning isn’t a reference to sexist stereotypes of women? Honestly, I can’t think of a single plot element that should prompt a warning for young women but not for young men, for the reasons stated above. Has anyone seen the movie? Any other speculation on what the warning refers to?