It doesn't bother me at all. I can't think of how this could be an issue unless the child is getting confused. Children generally know that there is a difference between girls and boys. I doubt that the child cares whether he/she is a girl or boy at this age. And it is possible that the child knows anyway. My kid can usually tell me if a person in a picture is a girl or boy by just looking at them. No nakedness needed. And he is only 3.
Also, this reminds me a little bit of that episode of Star Trek: TNG, where the whole planet was genderless but some of them wanted to actually identify as a specific gender. A lot of debates about gender identity and especially those stupid conversion therapies remind me of that episode. It was a great episode.