To put this in context, this recently published document is quite informative of the belief system you are seeing demonstrated. On the first page....
www.ucu.org.uk/media/10564/UCUs-position-on-Trans-inclusion/pdf/Trans_inclusion_November_2019.pdf
UCU position on trans inclusion
^UCU has a long history (from predecessor unions) of enabling members to selfidentify whether that is being black, disabled, LGBT+ or women. At recent Congress’ and further and higher education conferences, policy has been made on more options than binary genders on forms (FE conference 2017), using the acronym LGBT+ to ensure an inclusive approach to gender identities which is
different to that assigned at birth and/or their sexual identity being other than heterosexual (Congress 2017), gender-neutral toilets and facilities (Congress 2017), support campaigns to remove the requirement and practice of gender assignment at birth (Congress 2017), promotion of non heteronormative and non binary identities (FE conference 2014).^
So the bit I have highlighted is what this HR Director/Counsel and witness believes, that sex should disappear from birth certificates completely and only self ID of gender identity be legally relevant. The UCU are committed to eliminating sex on birth certificates.......
As are these academics.
futureoflegalgender.kcl.ac.uk/project/
So if you are a paying member of the UCU they are doing this in your name!