This is where Alex Drummond is coming from.
This is probably going to come out garbled, as I'm still working through the thought as I am typing.....
In a sense I agree with Alex Drummond and Danielle Muscato and all the bearers of 'lady penises'. (I have not gone mad - just hear me out!)
If, a transwoman is not and cannot become a woman, no matter what they do to themselves medically or surgically, and no matter how they present themselves in terms of name, dress, gendered behaviour, whether they do make those changes makes no difference to their sex. I argue that Danielle Muscato and Paris Lees are equally not women (and are therefore men) even though the former has not made any changes in outward presentation, whilst the latter has put a great deal of effort into achieving a highly and stereotypically feminised appearance. I consider them the same in that they both belong to the male sex.
So I am coming at it from this end. Alex, Danielle, et al are coming along the same path, but from the opposite direction. If you are a woman by virtue of the fact of having a internal female gender identity, your body is actually immaterial. It is your internal female gender that counts and that defines you. So if you were born into the 'wrong body', your body, whilst it may cause you emotional and psychological distress, is immaterial to you being a woman. Hence, there is no need to alter it in order to be a woman, because according to your definition of womanhood, you already are one. (Although you may choose to alter your body to alleviate any distress you experience.) According to this, Danielle and Paris are the same in that they are both women.
I agree with them that if transwomen are actual real women, then they are too. The point of disagreement is that I know that transwomen are not women. Womanhood resides in and is defined by biology, not an internal gendered identity. For them biology is irrelevant. For me biology is defining.