The reason you don’t hear this said is because why would anyone remark on it if there was no incongruity?
Contrary to your assertion you do have a gender identity, just as us trans folk have, but you utterly take that identity for granted and misunderstand its nature. Your gender expression, identity, and your biological sex likely align and are not worthy of remark. Congratulations you’re cisgender.
But for those of us who are trans our every interaction in your fixed binary society can be torturous.
It’s no surprise you don’t GET what being trans is, or how it feels, or how far it’s consequences run, how could you get it? You have no frame of reference. But does that preclude you displaying some sympathy, if not empathy?!