it's my understanding that Google has no Copyright to timsort's rangeCheck as it was borrowed from Java in the first place.

I don't think that was the point.

As I interpreted the article, the question was not whether Google could assert a copyright claim to that code; but rather whether Oracle (via Sun; via 'the Java entity') could assert copyright to code contributed to Java under the auspices of an Open Source contribution.

And whether the provenance of those particular lines of code could be categorically traced to an individual programmer employed by Sun.

For example, what if the programmer that originally typed those lines into a Java-associated file; was transcribing them from an example (written in Java or C or any other language) that he found kicking around on the internet; or in a book; or ...

The more trivial a piece of code is, the more likely that it has been written almost exactly the same by someone, or several someones, before. At which point it becomes "prior art" and explicitly excluded from enforceability, and provenance becomes key.

I believe that Google have admitted to the possibility of a common source in this case; but not to a direct copy. And that, combined with a lay jury, probably means it comes down to the persuasiveness of the lawyers rather than any stone-cold hard facts.