The whole point is they think the world should be treating them as the women they feel they are, allowing them to use women only spaces, re state the language we choose to use about ourselves and our female bodies, take women only awards, jobs and opportunities, sporting medals etc etc etc.
The thing is, though, they don't actually want to be treated like women. They want everyone to pretend that they are women, whilst treating them like the men they are, with the male privilege they believe they deserve.
If society actually treated them like women, we would be saying, "Women, know your place. The world does not revolve around you and your needs. You are not important. We don't care about your identity, to be perfectly honest we don't even care about your safety and dignity. We might claim to care, but the moment actually doing something about it inconveniences us in any way, we won't do it. We will say there are more important things. We will say that your wishes and needs and rights are trivial in the grand scheme of things, and there are more important things to worry about right now. Your will never get to the top of the list of important things to worry about. So just put up and shut up, nobody cares."
What gender critical feminists are saying to trans people is a far more gentle version of the above. What we are saying is more like, "Trans people, please be reasonable. You are not the only people whose needs should be considered. You are important, but you are not more important than others. Your identity is important to you, as ours is to us, and whilst your safety and dignity matters, so does ours. It's not that we don't care, but if caring about you requires us to put our own needs last, we don't think that is reasonable. We understand that your own rights are a high priority for you, just as ours are a high priority for us. If you stop fighting against us, we will stop fighting against you, but we cannot support you in your aims if it is to our own detriment. So please, be reasonable, discuss this with us like grown ups, and let's try to find a way to balance everyone's rights."
But they interpret the latter - which does represent a loss of male privilege from the point of view of someone who has grown up in a society built by and for the benefit of members of their own sex - as transphobia.
They are right that they are not being treated like women. But they are getting preferential treatment compared to women. If they actually were treated like women, they would not like it one bit.
Ironically, treating them like women would probably also greatly reduce their access to "gender affirming care", because the NHS would suddenly not have the budget for it anymore, and even trans people in their 30s would be told they could not have treatment which might cause the loss of their fertility, in case they change their mind about having children. (Which would be no bad thing, actually.) The medical profession treats adult women like children who aren't competent to make decisions about what happens to their own bodies, and trans identifying children like adults who are mature enough to give informed consent to anything.