I'm not sure why or how to turn it off, does anyone know?
(Also, insert weary photo of Kaczynski here.)
If unlock features remain after that, it's a manufacturer feature that's been set up. In that case you'll have to look for a guide for your specific brand and model.
Your phone can't turn this on by itself, if it's doing face recognition that means you set it up at some point.
It's like willingly walking through a minefield.