Really good question. What Google Ads is able to do is use the
Google Play Services to load ads from the web. This is a separate
app, and not blocked by default because it can break stuff.
To which I replied
Thanks for the reply, so even though apps are marked as Internet Access
off, they can get information from Google Play Services.
So my data in my files is safe as no data leaks out when internet access
in TC is turned off?
This is correct, and a disappointing limitation of Android.
Apps can exchange information with other apps, and thereby circumvent
the permission system.
So, from my experience if you don’t want an app to have internet access don’t rely on TC setting Internet Access off, turn off internet access in phone settings.
The worrying thing is apps sharing data and then your private data going on line via another app that has internet access.
So, where can I store documents on my phone that are totally secure?