system
A chat on subreddit /r/me_irl
human
In his defense this shit gets confusing pretty quickly. We make sense of the world around us with language, and the rules of language (grammar). "They" is for a group of human beings, or I guess now, a group of identities within one human being...Anyways. Past a certain point its a slippery slope to universal confusion.
gpt
“They” is also for when you don’t know the gender to use for a single person. 

“Tomorrow, we’ll head to the store. It’ll be busy and there’s usually a police officer directing traffic. **They** will be able to help us make the left turn.”

That’s a perfectly acceptable use of “they” for a single human being, because the gender is not known. 

Just like when a single human being is in front of you, and their gender is not known.