I don’t think the dot projector is used for anything other than authentication.
This implies that the dot projector is what makes the selfie camera a “True Depth” camera.
https://www.imore.com/how-iphone-x-camera-works
Apple also describes the dot projector as being an important feature of the True Depth camera, and what allows things like the new Snapchat filters to look so real. It makes sense that the data could be used for more accurate depth of field transitions as well.