If we used the "Killed By Google" criteria for hardware by other tech companies it would be significantly longer than 21. Of the products that made it past a tech demo, most were simply superseded by other hardware products, and many continued to work after the "killed" date (and some continue to work to this day).

As jsnell said in another comment on this article, the list is bad.

That list is so bad it is disingenuous. Because Google chooses to stop making a device doesn't mean it is "killed".