I don't think using the word delusion is helpful here. It's more useful I believe to break down words like gender, woman, man, etc. in order to find what people are ACTUALLY talking about. If someone says they are a woman, to some people it does not matter if they have a penis or were born XY, but to others it does, and it's much easier to discuss it in this fashion rather than to ask whether they "truly" are a woman or are just "deluding" themselves.