I feel like the true spirit of Google is that they test fifty shades of blue, then apply the "quantitatively best" shade of blue in an unrelated product where it makes the text unreadable. Either that or I have no idea what the heck they're testing for.
I strongly suspect that was an example of malicious compliance.
Googler #1: "Marissa want to change the link colors _again!_ What can we do to make her stop micromanaging shit like this?"
Googler #2: "All we need to do is convince her we are obviously wrong about 'graphic design-y things' because we're developers, and that she can prove we are wrong by making a 'data driven' decision. Then we'll say 'The only way to prove we are wrong would be an insane global 0 way multivariate test of all possible colours!!!' and she'll _insist_ on it. Then we build a tool and run the test and point at the results every time she tries to make us change it again. And we can offer to run the tool for _everything else_ she micromanages us about in future too!"
Googler #1: "Brilliant! So, do we build the tool and run the test? Or just make up the results and present them to her?"
For any company Google's size (including Google), it's rarely ever accurate to say "$COMPANY does $X". Maybe some parts of Google quantitatively tests everything, but it is safe to assume that there's huge variation across the company in testing rigor.
I'm not entirely convinced Google test _anything_.
Certainly not convinced enough to not play it up in the context of a snarky dis on Google and Googler culture.