I've done a lot of research about Protected Apps on Huawei phones. On phones like Huawei P8 when using background services or BroadcastReceivers the app should be added to Protected Apps list, otherwise, services or broadcast receivers get shut down in certain conditions:
- the app is closed from recents
- the phone is locked or sleeping
- etc
This list differs on different phones.
How are some apps automatically added to this section, such as Whatsapp or Piphon?
When installing one of those apps "Autorun" is checked by default, and when I go to Settings, I see it's added to Protected Apps list.