Please tell that to the people who cosplay Bloodelves, Night Elves, ... and other "slim" races at Blizzcon, while being FUCKING FAT PEOPLE. Those also fail miserably.
No, you 200pound American Woman cannot convincingly cosplay a borderline anorexic 80pound NE Druid.
Yet, many do and no one says shit.
But oh lord, a 80 pound - borderline anorexic - asian wants to cosplay a "sexy" Lich King version. Call the police.
It's more slutty if you dont have the body to wear "sexy clothes" (fat spilling everywhere - disgusting shit), than having a body and wearing sexy shit.
As you said: Look at bikini girls in swim baths.