And that “proof” is of a first generation Touch ID, and unless you can find a reliable citation showing where a dead finger would work, how do you know it’s “gobbledygook”?

From a practical standpoint, if someone was willing to cut off your finger, wouldn’t it be easier to just force you a gunpoint to unlock your phone? Someone who really wanted what’s on your phone bad enough to try the “unreliable” hack, would just force you to unlock your phone or give up the password.