A future update of the app might start phoning home.
People who are have the skills to investigate home phoning might get a version pushed that doesn't phone home.
/tinfoil
You don't even have to assume tinfoil hattery to think that a future update might phone home -- just a change in internal politics / leadership can lead to that.
Installing any kind of channel back to the FBI on an Android device from who-knows-where with who-knows-what malware running on it feels like a disaster waiting to happen.