info 'grails.app'
sets the info logging level for all classes that are in grails-app folder - like controllers, services, domain classes, taglibs etc.
If you want to set the info level for ALL classes, even third-party dependencies, you should set the root logger to this level:
import org.apache.log4j.Level
...
log4j = {
root ->
// root logger config
root.setLevel(Level.INFO)
}