It seems that in Android 6.0, Google has basically stated that they will not allow OEMs to hide battery information. Prior to this in older versions of Android, OEMs could hide battery stats for certain apps, meaning that if the OEM installed apps of their own that might be potentially battery draining, they could hide it from being displayed thus leading the user to believe that it might be a different app that’s causing the drain.
However according to Google, this will no longer be allowed in Android 6.0. The company writes, “A more accurate accounting and reporting of the power consumption provides the app developer both the incentives and the tools to optimize the power usage pattern of the application. Therefore, device implementations MUST be able to track hardware component power usage and attribute that power usage to specific applications.”
While it is targeted at OEMs, it is also good news for end-users as it basically means that a more transparent means of checking battery stats will be implemented, so that you know for sure what apps might be the cause of your battery drain.