I meant language is a living organism and artificial changes to it cannot be introduced or forced, they have to be adopted by the speakers naturally to take root. That requires the change to stem from a need felt or experienced by a majority.
The problem is that because of Ne, their gender identity in their mind is constantly changing so there is no way for the outsiders to know what gender they are feeling like at any given moment. So maybe it is they who should accommodate others in this case.
When to know if the mistake is not genuine, if they repeated it with a smug face when I corrected them, I would think it is deliberate. If I asked them to address me as "they" they would probably say "wtf?".
In the video below (when you play it), I would address the people as follows:
1) She but very difficult to tell apart, if they corrected me, I would not hesitate to address them as he
2) Definitely she
3) She
4) He