The problem openly talked about is that it puts limits on the extent of a transition. If TWAW then they are just a different kind of female, and so exclusion from other females is discrimination and rejection of their gender identity.
The answer to this is: sex does not change, and the limit to which a transition can be validated is other people's sex based rights.
Because otherwise you are (major issue 1) forcing compelled belief, compelled speech, (major issue 2) the hierarchy of male people's wishes over female people's rights and beliefs and (major issue 3) actual female bodily autonomy and consent, and no matter how you cut it up, it is (major issue 4) male supremacism because while insisting that male people are another kind of female there is a sex based group that has more rights and value than another sex based group. Not to mention (major issue 5) the right of females to perceive a person as they do, as opposed to basing their perception on what a male person chooses it to be, and all the issues of privacy, dignity, etc don't go away.
The unsaid bit: there are many reasons for transition. There is a sexual component for some TW, well evidenced. Female people (major issue 6) have a right not to be used for other people's sexual experiences. And yes, there is (major issue 7) no human right of a male to access to females. And let's be honest about this it is access to the physical presence of females, regardless of whether those females consent or not: no other part of the female but her physical form is required. So how can you say (major issue 8) this is not an entitlement for males to make use of female bodies for their own benefit? Where exactly is that bit in the human rights act?
Is this ok?
And that's before we even start on the multiple other major issues that we have to acknowledge that some males will use that access to actually and directly harm that female, who should have been in state care where there was an equal duty of care to her as well as to the male.
The line has to be: TWATW and that is great and all resources and facilities can be provided to support this.
The limits of transition are where female humans' sex based rights are affected. And 'no' is a word that adults have to learn to deal with, because no group of people is more important than another, and everyone has rights.