Even though it's going to need a 'live' /active finger for the access, just think of all the dumb thieves that are going to cut peoples thumbs and fingers off when they steal their iPhone now because they think they'll need their fingerprint..which won't work.
And yes, I'm being dead serious. You'll hear a story like this within 6 months of someone getting one of their fingers chopped off in the robbery with the phone.
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iMacs don't run each release of OSX, nor do PCs run each release of Windows. Their are minimum processor specs. Same with the iPhone.
Sorry but your argument just isn't sound.