And unicorns from Mars will invade the Earth. All it does is restate the test for pensions which was already decided over a decade ago. Honestly, I wish really wish I could make you understand how wrong you are but I give up.
It patently doesn't.
If it had, the Supreme Court would not have referred the question to the ECJ because it was settled law. It only reached ECJ because it wasn't settled law.
Essentially, the Government was arguing that because MB didn't have a GRC, that MB had sex = M and SPA = 60. This is how the Supreme Court summarised the situation:
On 31 May 2008 MB attained the age of 60. On 28 July 2008, she applied for a state retirement pension, backdated to 31 May 2008, on the footing that she was a woman. The application was rejected on 2 September 2008 on the ground that in the absence of a full gender recognition certificate, she could not be treated as a woman for the purpose of determining her pensionable age
ECJ has found that MB has sex = F (for social security) and passed it back to the Supreme Court to decide SPA.
In that regard, although, as it was noted in paragraph 29 of the present judgment, it is for the Member States to establish the conditions for legal recognition of a person’s change of gender, the fact remains that, for the purposes of the application of Directive 79/7, persons who have lived for a significant period as persons of a gender other than their birth gender and who have undergone a gender reassignment operation must be considered to have changed gender.
This is absolutely authority for the fact that sex can change without a GRC and authority for the proposition that if someone has surgery and lives as a woman that their sex is FEMALE for those matters within the scope of ECJ - notably social security, employment and services - because ECJ isn't going to decide that someone in that situation had a different sex for social security than services of employment because the principles for determination of sex are clearly the same.
And it is sex because that's the characteristic within scope of ECJ even if gender is used in the judgement.