Yes, that is – and has been to some extent for decades – a conventional truth. At anime, comic, and sci-fi cons, boys will be girls. 😆
But, you what? I’ve never cared; nor have most of us who attend the cons. It’s always been for laughs – and attention, but all cosplay is for that. It’s along the lines of a costume party, not real cross-dressing or transsexualism.