How would Apple even catch defective units? The rumor says they were returned, meaning they first shipped. Apple doesn't open every iPhone box to inspect the phone before selling it. This sounds very suspicious.
I'm with you. Steve Jobs never made such a vow. All he said was that their competitors were going down the wrong road with their 7" tablets running scaled up mobile phone software. iPad Mini doesn't do that.
Why do you assume Apple would require everyone to use the same finger all of the time? Apple has smart people and if they release this technology you can be sure they will have thought of things like that.