Not True. As the Forstater Tribunal demonstrated:
Paragraph 94 in Forstater v CGD Europe & others “The GRA provides for certain exceptions where, as a matter of law, a person’s gender is not the acquired gender… there is nothing in the Act that requires a person acting in any private capacity to refer to a person’s acquired gender or to refrain from referring to a person’s gender before it became the acquired gender.”
Sections 12, 15, and 16 of the Gender Recognition Act highlight some of the exceptions where even as a matter of law, a person is recognised as their biological sex:
Where even the law contains exceptions, in recognition of the clear scientific fact that humans are a sexually dimorphic (literally “two form”) species who do not exhibit sequential hermaphroditism, then it's obvious a person can't change sex.
The GRA provides a qualified right for males with the PC of gender reassignment to be treated as women, in most but not all circumstances. Hence why Matilda Simon is in line for male primogeniture and inheritance.