“They” is a very, very widely accepted gender-neutral fallback pronoun, acceptably used even in cases where the subject may not “identify as a they/them” or whatever phraseology has got you perturbed. Software developers should be especially aware of this as this makes writing user-facing content much easier. Any disagreement with this is almost certainly some sort of culture war issue, at best wrapped with a thin guide of “caring about proper English”. But thanks anyway.