Where are you getting that claim from? Google’s page says “users that access Google over IPv6”.
To me the specifically does not say, “could you” reach the servers but “did you”.
To me the specifically does not say, “could you” reach the servers but “did you”.
Because of Happy Eyeballs if you measure whether your users did use IPv6 you don't find out whether they could have done so, and so your results will be thrown off by happenstance.