I checked my phone to see if the same pattern is repeated. Under default settings, Youtube, Chrome, Google play store, and other services do send data to Google

I checked my phone to see if the same pattern is repeated. Under default settings, Youtube, Chrome, Google play store, and other services do send data to Google. You can disable it, there are options for disabling mobile data, wifi data, and background data. It wasnt as much as alluded to in the complaint, but essentially many apps that you may not suspect, including messaging, send small amount of data to Google whether on Wifi or Mobile data. Power users can always disable it, but would not have known until you see the complaint like this. One more thing: While the system apps do take up, even the apps which do not have permission to run in background use some amount of data. I have apps like amazon prime, Dominos, etc. which I have not opened in months (and restricted background activity) and yet they used some amount of data. If one good thing comes out of this, maybe they should restrict background activity until explicitly specified. (I do understand some of them would be for showing push notifications, but that can be handled differently)