I remember when Flurry was questioned about their dubious activation numbers before.
In 2014 report for instance, they laid out their methodology in which they estimated the new activation numbers based on "app download numbers" after the "supposed" activation. So Flurry actually has no access to the actual "activation number" -- they are just guessing from app downloads. They are not getting their data from Google, Apple, Verizon, AT&T, or others who actually activate phones (they are considered "trade secrets").
Considering that Apple has much more vibrant app ecosystem than competitors', Flurry's number could be off by 10% or 20% I'm guessing.