> do we think we're discovering that Chrome had more big holes than we thought or are we raising the security bar by fixing smaller holes?

To me the most probable explanation is that they automated a way to find (and fix) existing vulnerabilities in a way that was not possible before.

Some holes were probably very small, some were probably almost impossible to actually exploit, I don't doubt it. But still, I find it very hard to not consider this a strong security improvement overall (unless they made those numbers up)