The Equality Act 2010 rolled around 116 acts into one.
Most of the Equality Act 2010 was already in place in the previous anti-discrimination laws that it replaced. This includes the Race Relations Act 1976, the Sex Discrimination Act 1975, and the Disability Discrimination Act 1995.
Rather than continually using the phrase 'women and girls' or 'men and boys' exactly the same key as used in the 1975 act was provided for the Equality Act that 'woman' means a female of any age and 'man' means a male of any age.
www.legislation.gov.uk/ukpga/1975/65/enacted
From the 1975 Act
"Being a man is a genuine occupational qualification for a job only where—
(a)the essential nature of the job calls for a man for reasons of physiology (excluding physical strength or stamina) or, in dramatic performances or other entertainment, for reasons of authenticity, so that the essential nature of the job would be materially different if carried out by a woman ; or
(b)the job needs to be held by a man to preserve decency or privacy because—
(i)it is likely to involve physical contact with men in circumstances where they might reasonably object to its being carried out by a woman, or
(ii)the holder of the job is likely to do his work in circumstances where men might reasonably object to the presence of a woman because they are in a state of undress or are using sanitary facilities; or
(c)the nature or location of the establishment makes it impracticable for the holder of the job to live elsewhere than in premises provided by the employer, and—
(i)the only such premises which are available for persons holding that kind of job are lived in, or normally lived in, by men and are not equipped with separate sleeping accommodation for women and sanitary facilities which could be used by women in privacy from men
Sex in the 1975 Sex discrimination act is based on physiology, not identity or legal fictions.
"Physiology is the science of life. It is the branch of biology that aims to understand the mechanisms of living things, from the basis of cell function at the ionic and molecular level to the integrated behaviour of the whole body and the influence of the external environment."
It is, literally, laughable to pretend therefore that the Equality Act's definition of woman as 'a female of any age' (when replicating the 1975 Sex Discrimination Act definition) actually was meant to mean not exactly that but 'a female of any age but also including some men who call themselves women and who have a GRC and are legally 'female', some men who call themselves women and don't have a GRC but may or may not have requested to change the sex marker on their passport, not that you can ask to see a GRC anyway oh but not including those females who call themselves Men (with or without a GRC etc).