It's not just "Android was Linux-based", it was bought by Google in its current form as well.

No... it was bought by Google in a very primitive form, years before even its initial release. Android at the time of acquisition would be mostly unrecognizable today.

I don't think it's fair to say: "They only bought it so it doesn't count." You could just as easily say: "They only hired Paul Buchheit, he was the one who came up with GMail, not Google." Real inventions aren't spontaneous point events, they take many years of development, and can die anywhere along the way if you don't continuously create the necessary environment to foster them.