I said nothing at all about mental health professionals. Yes, they can certainly help. But emotional trauma never fully goes away, like a bruise or a cut does. It is a valid point to make a comparison to serious injury, which can leave scars and permanent disability, I will grant that. But someone who has undergone emotional trauma can never go back to their pre-traumatised state.
I am using the correct terms. AMAB and AFAB are standard in the transgender literature and in the community. And an OB-GYN will assign a gender according to the observation of the baby's genitals, not by randomisation. That's all straw on your part.
Yeah that's happened before, quite a few times. It has never caught on. They/them is easier to remember and has the benefit of being recognised as actual English words, used in an appropriate context. So yeah, vanishingly small, in practice.
Like I said, if you default to They/Them, almost nobody will complain.