I've come across this a lot. They think genes (and chromosomes) are like little manufacturer's marks inside your cells. Like the equivalent to the little debossed stamps you find on silver products:
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They are unaware of and uninterested in the concept of genes
doing anything. They've never given any thought to
why male chromosomes are different to female ones in humans, and how it relates to the body. They just assume different sex chromosomes are an irrelevant annoyance that gives power to ignorant transphobes, and nothing else.