I wonder if it was somehow accidentally "turned on" in packaging. Modern lithium batteries hold their charge for a really long time. I still have my iPhone 4 (the oldest iPhone I own). I turn it on once in a while. The battery, when the device is off, loses just a couple percentage points over a period of several months. So I don't buy that when the battery is dead, the device has been on a shelf for months. It very well may have been; but it's just not been my experience (for whatever little that's worth) that lithium batteries deplete that fast in storage.
Surely as millions of these roll off the line, and are tested, one ends up powered on, resting in it's little box, and arrives dead.