I'm a novice on the topic at hand, but isn't it also happens elsewhere, especially places where male still the main targets. Like video games? I think on "extra credit" did mentions about how game nowadays don't have a "
true female character" and the female characters in general are sexualised/stereotyped into societal traits that (male) audiences expected from them.
Similar issues can be found on lesbian character i guess (since we talked about Utena, and Aoi Hana, and my gaydar is tingling). It really hard to find a lesbian character where their sexualities are not their major traits, that dictate their personalities and on-screen activities. Off my head now is Rally from Gunsmith Cats, which her sexuality (which is unclear, but likely homo or bi !!) are very minor comparing to any other traits, or Utena, who mostly in the struggles against social gender pressures
In the end it's hard to design a good female characters for non-female audiences, or a good gay character for non-gay communities. So of course the industry will call on "screw it, let's go with sexualised stereotypes"