This is an expected behaviour because the class is an activity!
All classes that are mentioned in AndroidManifest.xml have to keep their names (activities, services, providers, receivers, application, instrumentation). Otherwise the system won't be able to find them.
Gradle build automatically generates some rules for your ProGuard configuration to achieve this. It scans AndroidManifest.xml and adds rules for each class found there.
If you want to see all the rules that are used, add this line to your ProGuard rules:
-printconfiguration "build/outputs/mapping/configuration.txt"
It will create configuration.txt
file containing all the rules.
There should be something like this:
# view AndroidManifest.xml #generated:50
-keep class com.github.browep.proguard.MainActivity {
<init>(...);
}