(disclaimer: work on maps, nothing to do with guides tho)
They never mentioned it in any of their emails, or the "newsletters" you get "access" to once you hit level 1.
Now, the grand reward (once you hit more than 500 points) is being a "trusted Google tester".
This is a joke and free work for Google. I will be contributing to OSM from now on.
(disclaimer: work on maps, nothing to do with guides tho)