You can't change sex. You can have surgery to present more typically in alignment with your chosen gender identity, but you cannot change sex. It is immutable. That is the ultimate conclusion of this judgment. Trans people are still protected as trans people under the law, but trans women are not protected as women.
What we need now is a revision of trans rights to protect trans people in public spaces, because the assumption that trans women are women and trans men are men has meant that actual protective legislation has been sidelined by these mantras. Fully medically transitioned trans women are not equipped to present the same threat to biological women as intact males are, and the law should reflect that.