My understanding is that a delusion is only classified as a delusion if it's in contradiction to what the person's community believes. So if you grew up in a cult that said you were the embodiment of a god, you believing it is not a delusion. So there's that.

Voices are real, to the person that hears them, and they may have concrete material causes in terms of how your brain works. Loads of otherwise hralthy people experience auditory hallucinations. Voices are only a problem if they interfere with your day to day function. For some they are quite helpful.

With an anorexic person the issue is less that they think they're fat and more that they restrict food to a dangerous degree.

So while I agree that trans people's feelings should not be allowed to harm others, and that they like everyone else need protection when their beliefs can cause them to harm themselves, I also believe it's unhelpful to say their beliefs are "not real".