Maybe it's a country/market "original"?

I had to think, but the few times I remember seeing "Netflix Original" for shows that I knew 100% were not original to Netflix, they were Canadian shows. Pretty sure they were Schitt's Creek, Continuum, and/or Orphan Black. Maybe Netflix was the only service carrying them in the US and that allowed them to call it an "original" with a straight face?

At least with Black Mirror, Netflix is producing them now. It's not "original" to them (like The Expanse wasn't original to Amazon) but at least they have an actual stake in it.

But yeah, I just ignore it lol.