What is the realistic difference now for someone who holds a GRC and someone who doesn't? What does it do beyond formally, legally recognise the transition?
Setting aside the burning need to protect female interests and female spaces from being the baby hurled out with the bathwater, not having a GRC currently doesn't prevent someone male from being able to request a transfer out of a male prison, to request different placement of hospital ward, to have all the needed rights for employment to present and have the name and recognition of transition, protection from harassment on basis of gender identity, to request a women's refuge placement - no one is even allowed to ask if the person holds a certificate, this is considered inappropriate and invasive.
Honestly, what is the difference? If it is just legal recognition then only 5000 people have applied for one, but many many more have changed their driving licences, bill names and all the rest of it. The GRC can't be that crucial? Certainly no one seems in the TWAW argument to be saying 'but only the ones with GRCs'.
Why can't there be another formal, legal means of registering a transition, identity and status as a TM, or TW, or NB? Which is not a legal fiction, and which doesn't in any way impinge on anyone else's reality or class or identity?