'They/them' has been used as a singular for many centuries. It's the least-worst option in English to express third person singular. It sounds strange when someone uses it to refer to a specific person, because we are used to gendered pronouns in that context. However, it's used ubiquitously to refer to nonspecific individuals.
'they' as a singular isn't my favorite thing in the world, but it doesn't matter much to me, and it clearly matters much, much more to some others. So, I think it's best to just use what pronouns folks prefer (within reason anyway).