> How do we know what the normal function is? How do we know how things are intended to work? (Intended by whom?)
Is this intentionally obtuse to prove a point? In the case of these conditions, a specific receptor in the body is not working properly. The receptor exists to bind to androgens and trigger downstream activity. In people with this condition, the receptor isn't properly activating in the presence of androgens. That receptor serves numerous functions in not only humans but across countless other species.
For an analogy, imagine you're trying to plug a device into an outlet in your country. Yet it doesn't fit. When you look at the prongs you discover it actually has 6 prongs pointing in random directions and can't possible fit into any standard outlet in your country. In fact, you can't even see how it would possibly work at all in any outlet anywhere because it doesn't make sense. It's safe to say that the connector isn't "normal". That's basically what's happening here. There's a clear and obvious version of what's typical, and it's likewise clear when a rare variant can't be observed to have some differences that can't possibly work. Meanwhile you can go anywhere else and observe typical plugs inserted into typical outlets and they're functioning typically.
There is a very clear "normal" in this case and it's easy to see how the receptors are supposed to work. Call it "typical" if that makes you feel better, but the medical community isn't using these terms for judgment or scorn.
There's a movement to pretend like we can't call anything "normal" lest we hurt someone's feelings. Yet most of these patients are discovered prior to the age of 10 (e.g. pre-puberty) because they seek treatment for various symptoms that they recognize as "not normal".