But those are the pronouns on all legal documents relating to this person. They have no grc , self id and rejecting pronouns count for nothing in the real world.
Well I am positive that Madigan has said on Twitter that they have both a GRC and a passport which says that they are female. Despite my views above on their credibility, I wouldn't be actually surprised if they do have a passport with female on it - they are actually fairly easy to get nowadays (you basically just need a note from your GP IIRC).
Anyway, legally, it doesn't really matter. If I turn up at work on Monday and say that I am going to reassign my gender and am eventually going to change my documents but I want everyone to start calling me Bob and addressing me using the pronouns 'he/him/his' now rather than 'she/her', they have to start doing that. As the law stands currently, they wouldn't be able to say 'We're not doing that until you get a GRC.' They might be able to take a short period of time to sort out the paperwork (eg get IT to give me a new email address in the name of Bob) but not long. I know I am discussing a work context here, but it's possible that the Equality Act has some application to MN too if it counts as a 'service' (which I think it arguably could, but the law relating to the internet is not a specialist subject of mine so am not 100% positive on that point).
You can also use 'they/them/their' etc. if you want.
I agree with Pratchet above that it feels like the transperson can dictate use of language in an entirely unnatural way. But it is what it is.