You are redefining women.
Denying this does not make it not true.
You are changing "womanhood" from a simple fact of the body to something that can be purely mental.
From something that has a clear line connecting the historic and sadly also comtempory disempowment, marginalisation and abuse of the female body with the existence and purpose of female-only protections and provisions, to something immaterial, hazy and self defined that cannot justify the existence of "woman-only" language and provisions but nevertheless not only demands access to them (thereby making them into mixed biological sex provisions and utterly undermining their entire raison d'etre) but also insists that female people who want to maintain female-only provisions, language, provisions or political voice may not do so, as evidenced by the TRA demands that OFCOM must find voicing the simple fact that trans women are male "transphobic".
Make no mistake, they want to make women simply saying why our sex matters impossible.
This is not the behaviour of an honest movement. This is the behaviour of a movement that, deep down, knows it is built on lies and the subjugation of female voices by male.
Of course, this was covered in great detail on the thread that you consider yourself above reading.
That poster was unable, or possibly just unwilling, to join the dots and accept that acting on his/her new, expanded definition of "woman" absolutely and undeniably changes the rights, protections, self knowledge, political voice and even historical story of female people. Like you, whenever they were confronted with the implications for female people of society accepting that there is a valid form of "womanhood" that can be nothing more than a mental difference between male people, he/she resorted to flat denial without any reasoning or substance to back it up.
I really recommend anyone who is reading your posts and thinking "hmmm, that sounds reasonable" reads the earlier thread where the flaws in that reasoning lie.
https://www.mumsnet.com/talk/womens_rights/5422838-what-is-trans-and-why-does-it-justify-undoing-sex-in-law-society-culture-and-history?page=1
Because the fact remains, any definition you go for that places more weight on a man's idea of himself as a woman than the embodied fact of female existence is simply not relevant to who women in the original female sense are and what women in the original female sense need at all.
No definition of woman that is stretched to include male people is more relevant to the needs and experiences and reality of female people than the simple old fashioned sex based definition, and there is sinply no way round that.