Numerous reviews claimed it was first gen. And while it may seem faster than iPhone 6, what you're feeling is the speed of the unlock due to the faster chip, not the sensor. Try this - wake the iPad from sleep with the sleep button, then quickly tap the home button without pressing it. And I do mean quickly, the fastest you can. The iPhone 6S would unlock after this while the iPad won't.
It's not how fast it unlocks - it's the time your finger needs to be on the button to register. I can just tap the 6S and wait to unlock (the unlock always takes a bit longer, but my finger doesn't have to remain on the button).
As you can see, this is not a big deal. It's not the speed that makes the second generation Touch ID better - it's reliability. The second generation is much more resistant to sweat and any type of wetness on fingers meaning it is much more reliable. On my old 6 and on my iPad I often try to unlock, it doesn't recognize my thumb, then I have to wipe it off my shirt, and sometimes even wipe the home button - and try again. This rarely happens on the new Touch ID, and in my case it's a better experience. I hope it comes to all Apple devices soon.
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As I said above, it's not the speed, it's the consistency of the unlock.