If someone who isn’t you scans their face, then types in the passcode (first of all, change your passcode), it won’t add their face, because it’s below a certainty threshold
iPhone Face ID tips - Do not reposition your face if face recognition failed.
If Face ID doesn’t recognize your face, don’t reposition your face so it will accept it. Instead, type in the passcode so it will ad that position of your face to the accepted data set
If someone who isn’t you scans their face, then types in the passcode (first of all, change your passcode), it won’t add their face, because it’s below a certainty threshold
If someone who isn’t you scans their face, then types in the passcode (first of all, change your passcode), it won’t add their face, because it’s below a certainty threshold