@BuffSoul
I mean, the new categories in athletics argument is completely reasonable given how much evidence there is to support the claim of blatant unfairness.
This however, is another thing. In the WN, they are refereed to constantly as being a girl. Also, this doesn't seem like the kind of manga to launch a PC campaign. Most likely, they were not specified as being a specific gender in the wording, so the TL just defaulted to male.
Also, when someone looks female and is actually male, at least in manga, they almost always are called out for it immediately, with MC giving a shocked reaction. And they also usually have a flat chest unless they are padding it with something and/or a clear reason is given otherwise. Since none was given this time and no shocked reaction was shown, it is assumed female. Additionally, this world also does not seem to contain the advanced medical sciences needed to replicate and implant opposing gender characteristics. Meaning those boobs should be naturally grown, something a male cant normally do (unless they are "moobs", caused by being very overweight, which clearly is not the case here).
So I am pretty sure this is a simple case caused by a lack of clarity, and an assumption. I could be wrong, but at least in the WN, the wish demon is a she.