It means homosexuality isn't unnatural. It means that a percentage of children in school are going to be gay. It's your claim that there's such a thing as a default human that objectively false which makes using it stupid as a basis for treating people unequally.
Wrong. That's the average human being, not the default human being. Those words don't mean the same thing. We grow hearts and arms and lungs because of hormones, proteins and genetics. Some humans, because of their particular genetics will default to being gay. That's perfectly natural and within the natural variation of human development.