Because after adding the same finger 3 times or even 300 times there comes a point you begin to question this security feature.
Since the replies here I found interesting articles on the uniqueness (or lack of) in fingerprints, how fingerprints are used to create algorithms to use on phone finger sensors, and some miscarriages of justice due to flaws in fingerprint research.
Why would I question it? It’s not recognizing new fingerprints. One scan isn’t any more or less secure and is likely even using most of the same points for verification. The only complaint may be the idea of diminishing returns with added effort. Plus, you can’t add 300 fingers if my memory serves. Isn’t it like 5 or so?
Much to do about nothing. Fingerprints are unique. The quality of the algorithms and methods of identifying one from another may be more or less accurate but you are REALLY thinking too hard about this.
Apple had a stat that said 1:1,000,000 or something like that. Which means - In theory - it could falsely recognize you. However, that is well beyond the “reasonable doubt” standard.
In terms of miscarriage of justice - I would suspect most of the miscarriages would be a result of mis-assumptions based on fingerprint evidence (like his fingerprint is on the door so he must have killed her). But I didn’t read your articles 🤷♂️
Interesting question but I’ve always appreciated the fact I could add the same finger twice. No idea how anyone could claim that’s a bad thing.