The article points out that Chaucer used "they" to refer to singular unknown person, so the usage is very old. It seems more respectful than assuming they are male.

I find myself wrong all the time, and I'm glad for the lesson!

Leaning on Chaucer isn't sufficient, because it was once a pronoun used for people:

https://en.wikipedia.org/wiki/It_(pronoun)

So maybe we should bring back it, or ignore Chaucer as an authority.