A disturbing Apple patent indicates that upcoming versions of the Face ID biometric technology could generate a map of the veins in a user's face. While Face ID already has a one in a million false-positive rate, vein mapping could dissuade hackers from attempting to use life-like masks to bypass Face ID.
https://www.notebookcheck.net/Vein-ID-Creepy-Apple-patent-indicates-that-new-versions-of-Face-ID-might-map-iPhone-and-iPad-users-facial-veins-to-fool-masked-hackers.482733.0.html
As long as it's done locally and doesn't get uploaded anywhere I'm not too against it.