Apple Let Suppliers Reduce Face ID Accuracy to Speed Up Production

It's selectivity was decent if you used just one finger, but decreased with enrolling multiple fingers. It was sensitive to skin oils building up, sensitive to sweat and moisture, and doesn't work with gloves.

FaceID improves upon all of that and permits apple to removie the button and giant borders everyone has griped about for years.

FaceID imrpoved on a number of things users said they didn't like. I'm not sure why people have a hard time accepting such.

I really do like the Fingerprint scanner, but all the things you listed were exactly right. The wetness and gloves were the biggest ones.
someone could chop off my finger and unlock my phone.

I do not believe this method has been documented as being true. But the evidence so far would say it isn't.

Based on what Apple has revealed regarding Touch ID and what the company's own patents have suggested, the sensor in the iPhone 5s utilizes two methods to sense and identify your fingerprint:
  • Capacitive -- A capacitive sensor is activated by the slight electrical charge running through your skin. We all have a small amount of electrical current running through our bodies, and capacitive technology utilizes that to sense touch. This is also the same technology used in the iPhone's touchscreen to detect input.
  • Radio frequency -- RF waves do not respond to the dead layer of skin on the outside of your finger -- the part that might be chapped or too dry to be read with much accuracy -- and instead reads only the living tissue underneath. This produces an extremely precise image of your print, and ensures that a severed finger is completely useless.