The religious view of gender and sex is too narrow. It ignores science and cannot adequately explain all aspects of gender and sex.
For example, genetic disorders can lead to children being born with both a penis and a vagina. How would religious leaders classify their sex? Their view of sex and gender is too narrow to acknowledge the existence of millions of people around the world which possess both male and female genitalia.
Also, Christians assert that if a person was born a certain way, then God intends them to remain that way. Yet, science tells us that even if someone was born anatomically female, their brain function can more closely resemble that of a male. God created our minds and our bodies, therefore, God intentionally created transgender people, and people whose brains identify with a gender which does not match their body.