Yeah, those examples are precisely what I mean. The article you linked to explains exactly what I mean, even stating that Shakespeare wouldn’t have used “they” if he knew the gender of the person he referred to.
The referents in these cases are general, not specific people. “Not a man” - no one, not referring to a specific person. “Some more audience than a mother” - someone else than a mother, not a specific person. “Each one” - not a specific person but every person.
If you look at dictionary definitions over the centuries, you’ll find singular they mentioned, but always specifically for this general meaning.
As an added note I don’t think it makes a difference if the current use is new or not, and it shouldn’t matter in this debate. Language changes all the time, even if people resist it.