I'm actually trying to unpick it.
If someone self ids as trans, Gib thinks that it's misgendering if others do not accept their chosen gender.
But if they subsequently obtain a GRC, with the minor gatekeeping requirements, they magically & in defiance of all available science, also change sex.
At this point any sceptics aren't misgendering that person, they are mis-sexing them.
This is clearly mildly bonkers.
However, it draws precisely the demarcation between 'self ids into chosen gender' & 'has gone through a gatekeeping process' which the same poster is loudly proclaiming to be not only unnecessary but also fundamentally transphobia.