[cderwin]

From a grammatical perspective it should be noted that "they" is plural. It is gender-neutral, but should only be used when referring to multiple people. The correct gender-neutral singular pronoun is "he or she".

[etjossem]

"They" can be used in the singular, and many communities use it in that manner frequently! Merriam-Webster has a great piece on this. [1]

[1] https://www.merriam-webster.com/words-at-play/singular-nonbi...

[grzm]

Singular they is indeed a thing:

https://en.wikipedia.org/wiki/Singular_they

Whether it's applicable in this case is another question.