Just blocking access to internet for this one app is not enough. It can use intents or a shared local storage with some other app to send the data out.

Great tool. Additionally, some Android forks (ColorOS) allow you to do this without apps, directly in the system settings of the app

The irony

App1 abuses notification permission

App2 keeps App1 in check

App3 to keep App2 from abusing network permission

...

TIL! What a find. Thanks mate!

I might actually try this now.