Not any longer. Today, it implies that the person concerned does not wish to be referred to as he or she. Language changes over time. I used to get really cross about the instruction "enjoy! ", because the verb to enjoy that I learnt required a subject. That's no longer the case. "They" has, like it or not, changed.
No. That is a new meaning being pushed hard by one particular group for their own ends (and to the detriment of many). It has not been settled and been agreed by the whole of society like the existing use has, hence the need for bullying and coercion to make it happen.
You can choose whatever words you want to use as long as misgendering never becomes illegal harassment, which it never should. What you can't choose is other people's reactions to the words you choose.
Clearly that’s not the case though - as you say yourself:
What you don't have is the right not to seem, in some people's eyes, in some situations (eg insisting on calling a colleague who has politely requested that you refer to them in emails as they), unnecessarily confrontational.
by calling our use of correct sex pronouns “unnecessarily confrontational” you are attempting to coerce our language. Your comment about not being able to control other people’s reactions to the words we choose - that sounds a bit like when the tras claim that we have free speech but there may be ‘consequences’ that we don’t like (like getting bullied, sacked, harassed and physically harmed).
Feel free not to continue engaging with me and agree to disagree - I won’t take it as rude at all but it may be worth considering how your position on pronoun use can be seen as coercive.
Also read Pronouns Are Rohypnol by Barbara Kerr to understand the issue more thoroughly.